According to the scheme of classification, Philosophy is divided into a. Phenomenology; b. Normative Science; c. Metaphysics.
Phenomenology ascertains and studies the kinds of elements universally present in the phenomenon; meaning by the phenomenon, whatever is present at any time to the mind in any way. Normative science distinguishes what ought to be from what ought not to be, and makes many other divisions and arrangements subservient to its primary dualistic distinction. Metaphysics seeks to give an account of the universe of mind and matter. (CP1-186)

Phenomenology is the first division of philosophy. Phaneroscopy is the description of the phaneron (phenomenon); and by the phaneron I mean the collective total of all that is in any way or in any sense present to the mind, quite regardless of whether it corresponds to any real thing or not. … Those features of the phaneron that I have found in my mind are present at all times and to all minds. (CP1-284)

What I term phaneroscopy is that study which, supported by the direct observation of phanerons and generalizing its observations, signalizes several very broad classes of phanerons; describes the features of each; shows that although they are so inextricably mixed together that no one can be isolated, yet it is manifest that their characters are quite disparate; then proves, beyond question, that a certain very short list comprises all of these broadest categories of phanerons there are; and finally proceeds to the laborious and difficult task of enumerating the principal subdivisions of those categories. (CP1-286)

I believe in inventing new philosophical words in order to avoid the ambiguities of the familiar words. I use the word phaneron to mean all that is present to the mind in any sense or in any way whatsoever, regardless of whether it be fact or figment. I examine the phaneron and I endeavor to sort out its elements according to the complexity of their structure. I thus reach my three categories.(CP8-213)

It will be plain from what has been said that phaneroscopy has nothing at all to do with the question of how far the phanerons it studies correspond to any realities. It religiously abstains from all speculation as to any relations between its categories and physiological facts, cerebral or other. It does not undertake, but sedulously avoids, hypothetical explanations of any sort. It simply scrutinizes the direct appearances, and endeavors to combine minute accuracy with the broadest possible generalization. The student's great effort is not to be influenced by any tradition, any authority, any reasons for supposing that such and such ought to be the facts, or any fancies of any kind, and to confine himself to honest, single-minded observation of the appearances. The reader, upon his side, must repeat the author's observations for himself, and decide from his own observations whether the author's account of the appearances is correct or not. (CP1-287)

The list of categories, or as Harris, the author of Hermes, called them, the "philosophical arrangements," is a table of conceptions drawn from the logical analysis of thought and regarded as applicable to being. This description applies not merely to the list published by me in 1867, and which I here endeavor to amplify, but also to the categories of Aristotle and to those of Kant. The latter have been more or less modified by different critics, as Renouvier, and still more profoundly by Hegel. My own list grew originally out of the study of the table of Kant. (CP1-300)
Aristotle listed ten categories and Kant twelve; Peirce simply listed three: Firstness, Secondness, and Thirdness.

Peirce’s phenomenological categories and his architectonic view of science are important to understand but are presented in a scattered fashion in the lectures. Sandia Report/Philip L. Campbell has collated this material here (Table 1) for ease of comparison and reference.

Trichotomy

Perhaps I might begin by noticing how different numbers have found their champions. Two was extolled by Peter Ramus, Four by Pythagoras, Five by Sir Thomas Browne, and so on. For my part, I am a determined foe of no innocent number; I respect and esteem them all in their several ways; but I am forced to confess to a leaning to the number Three in philosophy. In fact, I make so much use of threefold divisions in my speculations, that it seems best to commence by making a slight preliminary study of the conceptions upon which all such divisions must rest. I mean no more than the ideas of first, second, third -- ideas so broad that they may be looked upon rather as moods or tones of thought, than as definite notions, but which have great significance for all that. Viewed as numerals, to be applied to what objects we like, they are indeed thin skeletons of thought, if not mere words. If we only wanted to make enumerations, it would be out of place to ask for the significations of the numbers we should have to use; but then the distinctions of philosophy are supposed to attempt something far more than that; they are intended to go down to the very essence of things, and if we are to make one single threefold philosophical distinction, it behooves us to ask beforehand what are the kinds of objects that are first, second, and third, not as being so counted, but in their own true characters. That there are such ideas of the really first, second, and third, we shall presently find reason to admit. (CP1-355)

"Trichotomy"

The first is that whose being is simply in itself, not referring to anything nor lying behind anything. The second is that which is what it is by force of something to which it is second. The third is that which is what it is owing to things between which it mediates and which it brings into relation to each other. (CP1-356)

The idea of the absolutely first must be entirely separated from all conception of or reference to anything else; for what involves a second is itself a second to that second. The first must therefore be present and immediate, so as not to be second to a representation. It must be fresh and new, for if old it is second to its former state. It must be initiative, original, spontaneous, and free; otherwise it is second to a determining cause. It is also something vivid and conscious; so only it avoids being the object of some sensation. It precedes all synthesis and all differentiation; it has no unity and no parts. It cannot be articulately thought: assert it, and it has already lost its characteristic innocence; for assertion always implies a denial of something else. Stop to think of it, and it has flown! What the world was to Adam on the day he opened his eyes to it, before he had drawn any distinctions, or had become conscious of his own existence -- that is first, present, immediate, fresh, new, initiative, original, spontaneous, free, vivid, conscious, and evanescent. Only, remember that every description of it must be false to it. (CP1-357)

Just as the first is not absolutely first if thought along with a second, so likewise to think the second in its perfection we must banish every third. The second is therefore the absolute last. But we need not, and must not, banish the idea of the first from the second; on the contrary, the second is precisely that which cannot be without the first. It meets us in such facts as another, relation, compulsion, effect, dependence, independence, negation, occurrence, reality, result. A thing cannot be other, negative, or independent, without a first to or of which it shall be other, negative, or independent. Still, this is not a very deep kind of secondness; for the first might in these cases be destroyed yet leave the real character of the second absolutely unchanged. When the second suffers some change from the action of the first, and is dependent upon it, the secondness is more genuine. But the dependence must not go so far that the second is a mere accident or incident of the first; otherwise the secondness again degenerates. The genuine second suffers and yet resists, like dead matter, whose existence consists in its inertia. Note, too, that for the second to have the finality that we have seen belongs to it, it must be determined by the first immovably, and thenceforth be fixed; so that unalterable fixity becomes one of its attributes. We find secondness in occurrence, because an occurrence is something whose existence consists in our knocking up against it. A hard fact is of the same sort; that is to say, it is something which is there, and which I cannot think away, but am forced to acknowledge as an object or second beside myself, the subject or number one, and which forms material for the exercise of my will.
The idea of second must be reckoned as an easy one to comprehend. That of first is so tender that you cannot touch it without spoiling it; but that of second is eminently hard and tangible. It is very familiar, too; it is forced upon us daily; it is the main lesson of life. In youth, the world is fresh and we seem free; but limitation, conflict, constraint, and secondness generally, make up the teaching of experience. With what firstness "The scarfed bark puts from her native bay;" with what secondness "doth she return, With overweathered ribs and ragged sails."
But familiar as the notion is, and compelled as we are to acknowledge it at every turn, still we never can realize it; we never can be immediately conscious of finiteness, or of anything but a divine freedom that in its own original firstness knows no bounds. (CP1-358)

First and second, agent and patient, yes and no, are categories which enable us roughly to describe the facts of experience, and they satisfy the mind for a very long time. But at last they are found inadequate, and the third is the conception which is then called for. The third is that which bridges over the chasm between the absolute first and last, and brings them into relationship. We are told that every science has its qualitative and its quantitative stage; now its qualitative stage is when dual distinctions -- whether a given subject has a given predicate or not --suffice; the quantitative stage comes when, no longer content with such rough distinctions, we require to insert a possible halfway between every two possible conditions of the subject in regard to its possession of the quality indicated by the predicate. Ancient mechanics recognized forces as causes which produced motions as their immediate effects, looking no further than the essentially dual relation of cause and effect. That was why it could make no progress with dynamics. The work of Galileo and his successors lay in showing that forces are accelerations by which [a] state of velocity is gradually brought about. The words "cause" and "effect" still linger, but the old conceptions have been dropped from mechanical philosophy; for the fact now known is that in certain relative positions bodies undergo certain accelerations. Now an acceleration, instead of being like a velocity a relation between two successive positions, is a relation between three; so that the new doctrine has consisted in the suitable introduction of the conception of threeness. On this idea, the whole of modern physics is built. The superiority of modern geometry, too, has certainly been due to nothing so much as to the bridging over of the innumerable distinct cases with which the ancient science was encumbered; and we may go so far as to say that all the great steps in the method of science in every department have consisted in bringing into relation cases previously discrete. (CP1-359)

We have seen that it is the immediate consciousness that is preeminently first, the external dead thing that is preeminently second. In like manner, it is evidently the representation mediating between these two that is preëminently third. Other examples, however, should not be neglected. The first is agent, the second patient, the third is the action by which the former influences the latter. Between the beginning as first, and the end as last, comes the process which leads from first to last. (CP1-361)

But it will be asked, why stop at three? Why not go on to find a new conception in four, five, and so on indefinitely? The reason is that while it is impossible to form a genuine three by any modification of the pair, without introducing something of a different nature from the unit and the pair, four, five, and every higher number can be formed by mere complications of threes. To make this clear, I will first show it in an example. The fact that A presents B with a gift C, is a triple relation, and as such cannot possibly be resolved into any combination of dual relations. Indeed, the very idea of a combination involves that of thirdness, for a combination is something which is what it is owing to the parts which it brings into mutual relationship. But we may waive that consideration, and still we cannot build up the fact that A presents C to B by any aggregate of dual relations between A and B, B and C, and C and A. A may enrich B, B may receive C, and A may part with C, and yet A need not necessarily give C to B. For that, it would be necessary that these three dual relations should not only coexist, but be welded into one fact.
Thus we see that a triad cannot be analyzed into dyads.
But now I will show by an example that a four can be analyzed into threes. Take the quadruple fact that A sells C to B for the price D. This is a compound of two facts:
*first, that A makes with C a certain transaction, which we may name E; and
*second, that this transaction E is a sale of B for the price D.
Each of these two facts is a triple fact, and their combination makes up [as] genuine [a] quadruple fact as can be found.
The explanation of this striking difference is not far to seek. A dual relative term, such as "lover" or "servant," is a sort of blank form, where there are two places left blank.
I mean that in building a sentence round "lover," as the principal word of the predicate, we are at liberty to make anything we see fit the subject, and then, besides that, anything we please the object of the action of loving.
But a triple relative term such as "giver" has two correlates, and is thus a blank form with three places left blank. Consequently, we can take two of these triple relatives and fill up one blank place in each with the same letter, X, which has only the force of a pronoun or identifying index, and then the two taken together will form a whole having four blank places; and from that we can go on in a similar way to any higher number. But when we attempt to imitate this proceeding with dual relatives, and combine two of them by means of an X, we find we only have two blank places in the combination, just as we had in either of the relatives taken by itself. A road with only three-way forkings may have any number of termini, but no number of straight roads put end on end will give more than two termini. Thus any number, however large, can be built out of triads; and consequently no idea can be involved in such a number, radically different from the idea of three. I do not mean to deny that the higher numbers may present interesting special configurations from which notions may be derived of more or less general applicability; but these cannot rise to the height of philosophical categories so fundamental as those that have been considered. (CP 1-363)

"Peirce's Trichotomy"

Peirce's Categories

*Image sources:* www.minutesemeiotic.org

Firstness, Secondness and Thirdness

Our experiences have raw qualitative characters which do not directly involve relation with other things: they exhibit firstness.
They also stand in relations to each other, interacting against one another and so on: this involves secondness, as when fire immediately follows our dropping the sodium in hot water.
But we are aware that this interaction is intelligible, it is ‘mediated’: we can bring it down into a continuous spread of small changes which go together to make up the big one; and we are aware that it conforms to a law. Finding it intelligible introduces thirdness: we understand the two elements of the interaction by reference to a third mediating fact.

The aim of inquiry, for Peirce, is to find the thirdness (law and pattern) in the manifold of sensory experiences that we undergo.
The norms employed by the scientific method are to be vindicated by showing how they provide means for finding more and more pattern and mediation (more and more thirdness) in the world of our experience.

FIRSTNESS

The first is predominant in feeling, as distinct from objective perception, will, and thought. (CP1-302)

QUALITIES OF FEELING
There are certain qualities of feeling, such as the color of magenta, the odor of attar, the sound of a railway whistle, the taste of quinine, the quality of the emotion upon contemplating a fine mathematical demonstration, the quality of feeling of love, etc. I do not mean the sense of actually experiencing these feelings, whether primarily or in any memory or imagination. That is something that involves these qualities as an element of it. But I mean the qualities themselves which, in themselves, are mere may-bes, not necessarily realized. … it means just what it means when I say that aniline red is red. That mere quality, or suchness, is not in itself an occurrence, as seeing a red object is; it is a mere may-be. (CP1-304)

FEELING AS INDEPENDENT OF MIND AND CHANGE
Suppose I begin by inquiring of you, Reader, in what particulars a feeling of redness or of purple without beginning, end, or change; or an eternally sounding and unvarying railway whistle; or a sempiterne thrill of joyous delight …. I suppose you will tell me that no such thing could be alone in the universe because,
firstly, it would require a mind to feel it, which would not be the feeling itself;
secondly, the color or sound and probably also the thrill of delight would consist of vibrations;
thirdly, none of them could last forever without a flow of time;
fourthly, each would have a quality, which would be a determination in several respects, the color in hue, luminosity, chroma, and vividness; the sound in pitch, timbre (itself highly complex), loudness, and vividness; the delight more or less sensual, more or less emotional, more or less elevated, etc.;
fifthly, each would require a physical substratum altogether disparate to the feeling itself. (CP1-305)

A DEFINITION OF FEELING
By a feeling, I mean an instance of that kind of consciousness which involves no analysis, comparison or any process whatsoever, nor consists in whole or in part of any act by which one stretch of consciousness is distinguished from another, which has its own positive quality which consists in nothing else, and which is of itself all that it is, however it may have been brought about; so that if this feeling is present during a lapse of time, it is wholly and equally present at every moment of that time. To reduce this description to a simple definition, I will say that by a feeling I mean an instance of that sort of element of consciousness which is all that it is positively, in itself, regardless of anything else. (CP1-306)

A feeling, then, is not an event, a happening, a coming to pass, since a coming to pass cannot be such unless there was a time when it had not come to pass; and so it is not in itself all that it is, but is relative to a previous state. A feeling is a state, which is in its entirety in every moment of time as long as it endures. But a feeling is not a single state which is other than an exact reproduction of itself. For if that reproduction is in the same mind, it must be at a different time, and then the being of the feeling would be relative to the particular time in which it occurred, which would be something different from the feeling itself, violating the definition which makes the feeling to be all that it is regardless of anything else. Or, if the reproduction were simultaneous with the feeling, it must be in another mind, and thus the identity of the feeling would depend upon the mind in which it was, which is other than the feeling; and again the definition would be violated in the same way. Thus, any feeling must be identical with any exact duplicate of it, which is as much as to say that the feeling is simply a quality of immediate consciousness. (CP1-307)

But it must be admitted that a feeling experienced in an outward sensation may be reproduced in memory. ... For instance, you experience a certain color sensation due to red-lead. It has a definite hue, luminosity, and chroma. These [are] three elements -- which are not separate in the feeling, it is true, and are not, therefore, in the feeling at all, but are said to be in it, as a way of expressing the results which would follow, according to the principles of chromatics, from certain experiments with a color disk, color-box, or other similar apparatus. In that sense, the color sensation which you derive from looking at the red-lead has a certain hue, luminosity, and chroma which completely define the quality of the color. The vividness, however, is independent of all three of these elements; and it is very different in the memory of the color a quarter of a second after the actual sensation from what it is in the sensation itself, although this memory is conceivably perfectly true as to hue, luminosity, and chroma, which truth constitutes it an exact reproduction of the entire quality of the feeling. (CP1-308)

It follows that since the vividness of a feeling -- which would be more accurately described as the vividness of a consciousness of the feeling -- is independent of every component of the quality of that consciousness, and consequently is independent of the resultant of those components, which resultant quality is the feeling itself. We thus learn what vividness is not; and it only remains to ascertain what else it is. (CP1-309)

To this end two remarks will be useful.
1. The first is that of whatever is in the mind in any mode of consciousness there is necessarily an immediate consciousness and consequently a feeling.
All that is immediately present to a man is what is in his mind in the present instant. His whole life is in the present. If he asks what is the content of the present instant, his question always comes too late. The present has gone by. (CP1-310)
2. Every operation of the mind, however complex, has its absolutely simple feeling. This is a secondary feeling or sensation excited from within the mind, just as the qualities of outward sense are excited by something psychic without us. (CP1-311)

THE COMMUNICABILITY OF FEELINGS
Philosophers, who very properly call all things into question, have asked whether we have any reason to suppose that red looks to one eye as it does to another. I answer that slight differences there may be, but [consider the blind man imagining] red to resemble the blare of a trumpet. He had collected that notion from hearing ordinary people converse together about colors, and since I was not born to be one of those whom he had heard converse, the fact that I can see a certain analogy, shows me not only that my feeling of redness is something like the feelings of the persons whom he had heard talk, but also his feeling of a trumpet's blare was very much like mine. I am confident that a bull and I feel much alike at the sight of a red rag. As for the senses of my dog, I must confess that they seem very unlike my own, but when I reflect to how small a degree he thinks of visual images, and of how smells play a part in his thoughts and imaginations analogous to the part played by sights in mine, I cease to be surprised that the perfume of roses or of orange flowers does not attract his attention at all and that the effluvia that interest him so much, when at all perceptible to me, are simply unpleasant. He does not think of smells as sources of pleasure and disgust but as sources of information, just as I do not think of blue as a nauseating color, nor of red as a maddening one. I know very well that my dog's musical feelings are quite similar to mine though they agitate him more than they do me. He has the same emotions of affection as I, though they are far more moving in his case. You would never persuade me that my horse and I do not sympathize, or that the canary bird that takes such delight in joking with me does not feel with me and I with him; and this instinctive confidence of mine that it is so, is to my mind evidence that it really is so. My metaphysical friend who asks whether we can ever enter into one another's feelings -- and one particular sceptic whom I have in mind is a most exceptionally sympathetic person, whose doubts are born of her intense interest in her friends -- might just as well ask me whether I am sure that red looked to me yesterday as it does today and that memory is not playing me false. I know experimentally that sensations do vary slightly even from hour to hour; but in the main the evidence is ample that they are common to all beings whose senses are sufficiently developed. (CP1-314)

TRANSITION TO SECONDNESS
The whole content of consciousness is made up of qualities of feeling, as truly as the whole of space is made up of points or the whole of time of instants. (CP1-317)

Contemplate anything by itself -- anything whatever that can be so contemplated. Attend to the whole and drop the parts out of attention altogether. One can approximate nearly enough to the accomplishment of that to see that the result of its perfect accomplishment would be that one would have in his consciousness at the moment nothing but a quality of feeling. This quality of feeling would in itself, as so contemplated, have no parts. It would be unlike any other such quality of feeling. In itself, it would not even resemble any other; for resemblance has its being only in comparison. It would be a pure priman. Since this is true of whatever we contemplate, however complex may be the object, it follows that there is nothing else in immediate consciousness. To be conscious is nothing else than to feel.(CP1-318)

SECONDNESS

The second category that I find, the next simplest feature common to all that comes before the mind, is the element of struggle. By struggle I mean mutual action between two things regardless of any sort of third or medium, and in particular regardless of any law of action. (CP1-322)

Action and Perception:
When you put your shoulder against a door and try to force it open, you have a sense of resistance and at the same time a sense of effort. There can be no resistance without effort; there can be no effort without resistance. They are only two ways of describing the same experience. It is a double consciousness. We become aware of ourself in becoming aware of the not-self. The waking state is a consciousness of reaction; and as the consciousness itself is two-sided, so it has also two varieties; namely, action, where our modification of other things is more prominent than their reaction on us, and perception, where their effect on us is overwhelmingly greater than our effect on them. And this notion, of being such as other things make us, is such a prominent part of our life that we conceive other things also to exist by virtue of their reactions against each other. The idea of other, of not, becomes a very pivot of thought. To this element I give the name of Secondness. (CP1-324)

The Varieties of Secondness:
The idea of second is predominant in the ideas of causation and of statical force. For cause and effect are two; and statical forces always occur between pairs. Constraint is a Secondness. In the flow of time in the mind, the past appears to act directly upon the future, its effect being called memory, while the future only acts upon the past through the medium of thirds. Phenomena of this sort in the outward world shall be considered below. In sense and will, there are reactions of Secondness between the ego and the non-ego (which non-ego may be an object of direct consciousness). In will, the events leading up to the act are internal, and we say that we are agents more than patients. In sense, the antecedent events are not within us; and besides, the object of which we form a perception (though not that which immediately acts upon the nerves) remains unaffected. Consequently, we say that we are patients, not agents. In the idea of reality, Secondness is predominant; for the real is that which insists upon forcing its way to recognition as something other than the mind's creation. (Remember that before the French word, second, was adopted into our language, other was merely the ordinal numeral corresponding to two.) The real is active; we acknowledge it, in calling it the actual. (This word is due to Aristotle's use of {energeia}, action, to mean existence, as opposed to a mere germinal state.) Again, the kind of thought of those dualistic philosophers who are fond of laying down propositions as if there were only two alternatives, and no gradual shading off between them, as when they say that in trying to find a law in a phenomenon I commit myself to the proposition that law bears absolute sway in nature, such thought is marked by Secondness. (CP1-325)

Polar Distinctions and Volition:
Polar Distinctions
Any distinction between two equally decided characters to which no third seems to be coördinate (although a neutrality separates them). Examples are that of past and future, with the resulting two ways of passing over a line (and consequent right-and left-handed spirals and helices, whence probably the magnetic and possibly the electric poles -- supposing the latter to be truly "polar" in our sense), with the right and left sides of our bodies, and the two sexes, seems pretty much to exhaust the list of them.
Volition
In psychology, polar distinctions abound, most of them referring to volition. Thus, pleasure is any kind of sensation that one immediately seeks, pain any that one immediately shuns. Right and wrong are expressly volitional. (CP1-330)

Ego and Non-Ego:
The triad, feeling, volition, cognition
Feeling is a quality, but so far as there is mere feeling, the quality is not limited to any definite subject. We hear of a man whose mind is jaundiced. That phrase well expresses feeling without reason. Feeling also as such is unanalyzed.
Volition is through and through dual. There is the duality of agent and patient, of effort and resistance, of active effort and inhibition, of acting on self and on external objects. Moreover, there is active volition and passive volition, or inertia, the volition of reform and the volition of conservatism.
That shock which we experience when anything particularly unexpected forces itself upon our recognition (which has a cognitive utility as being a call for explanation of the presentment), is simply the sense of the volitional inertia of expectation, which strikes a blow like a water-hammer when it is checked; and the force of this blow, if one could measure it, would be the measure of the energy of the conservative volition that gets checked.
Low grades of this shock doubtless accompany all unexpected perceptions; and every perception is more or less unexpected. Its lower grades are, as I opine, not without experimental tests of the hypothesis, that sense of externality, of the presence of a non-ego, which accompanies perception generally and helps to distinguish it from dreaming. This is present in all sensation, meaning by sensation the initiation of a state of feeling; -- for by feeling I mean nothing but sensation minus the attribution of it to any particular subject. In my use of words, when an ear-splitting, soul-bursting locomotive whistle starts, there is a sensation, which ceases when the screech has been going on for any considerable fraction of a minute; and at the instant it stops there is a second sensation. Between them there is a state of feeling. (CP1-332)

As for volition, I would limit the term in one way and extend it in another. I would limit it to the momentary direct dyadic consciousness of an ego and a non-ego then and there present and reacting each upon the other. In one, the action is generally more active, in the other more passive; but precisely what this difference consists in I do not feel sure. I think, however, that the will to produce a change is active, the will to resist a change is passive. All sensation is essentially, by its very definition, active. The objection to this is that, according to it, the voluntary inhibition of a reflex should not give a sense of effort; and probably the definition of the distinction between the sense of externality in willing and in requires a supplement or other slight modification on this account. But the important point [is] that the sense of externality in perception consists in a sense of powerlessness before the overwhelming force of perception. Now the only way in which any force can be learned is by something like trying to oppose it. That we do something like this is shown by the shock we receive from any unexpected experience. It is the inertia of the mind, which tends to remain in the state in which it is. No doubt there is a marked difference between the active and intentional volition of muscular contraction and the passive and unintentional volition that gives the shock of surprise and the sense of externality. But the two are to be classed together as alike modes of double consciousness, that is, of awareness, at once and in the same awareness, of an ego and a non-ego. . . .(CP1-334)

We perceive objects brought before us; but that which we especially experience -- the kind of thing to which the word "experience" is more particularly applied -- is an event. We cannot accurately be said to perceive events; for this requires what Kant called the "synthesis of apprehension," not however, by any means, making the needful discriminations. A whistling locomotive passes at high speed close beside me. As it passes the note of the whistle is suddenly lowered from a well-understood cause. I perceive the whistle, if you will. I have, at any rate, a sensation of it. But I cannot be said to have a sensation of the change of note. I have a sensation of the lower note. But the cognition of the change is of a more intellectual kind. That I experience rather than perceive. It is [the] special field of experience to acquaint us with events, with changes of perception. Now that which particularly characterizes sudden changes of perception is a shock. A shock is a volitional phenomenon. The long whistle of the approaching locomotive, however disagreeable it may be, has set up in me a certain inertia, so that the sudden lowering of the note meets with a certain resistance. That must be the fact; because if there were no such resistance there could be no shock when the change of note occurs. Now this shock is quite unmistakable. It is more particularly to changes and of perception that we apply the word "experience." We experience vicissitudes, especially. We cannot experience the vicissitude without experiencing the perception which undergoes the change; but the concept of experience is broader than that of perception, and includes much that is not, strictly speaking, an object of perception. It is the compulsion, the absolute constraint upon us to think otherwise than we have been thinking that constitutes experience. Now constraint and compulsion cannot exist without resistance, and resistance is effort opposing change. Therefore there must be an element of effort in experience; and it is this which gives it its peculiar character. But we are so disposed to yield to it as soon as we can detect it, that it is extremely difficult to convince ourselves that we have exerted any resistance at all. It may be said that we hardly know it except through the axiom that there can be no force where there is no resistance or inertia. Whoever may be dissatisfied with my statement will do well to sit down and cipher out the matter for himself. He may be able to formulate the nature of the oppositional element in experience, and its relation to ordinary volition better than I have done; but that there is an oppositional element in it, logically not easily distinguished from volition, will, I make no doubt at all, be his ultimate conclusion.(CP1-336)

THIRDNESS

Examples of Thirdness
By the third, I mean the medium or connecting bond between the absolute first and last. The beginning is first, the end second, the middle third. The end is second, the means third. The thread of life is a third; the fate that snips it, its second. A fork in a road is a third, it supposes three ways; a straight road, considered merely as a connection between two places is second, but so far as it implies passing through intermediate places it is third. Position is first, velocity or the relation of two successive positions second, acceleration or the relation of three successive positions third. But velocity in so far as it is continuous also involves a third. Continuity represents Thirdness almost to perfection. Every process comes under that head. Moderation is a kind of Thirdness. The positive degree of an adjective is first, the superlative second, the comparative third. All exaggerated language, "supreme," "utter," "matchless," "root and branch," is the furniture of minds which think of seconds and forget thirds. Action is second, but conduct is third. Law as an active force is second, but order and legislation are third. Sympathy, flesh and blood, that by which I feel my neighbor's feelings, is third. (CP1-337)

Representation and Generality
The ideas in which Thirdness is predominant are, as might be expected, more complicated, and mostly require careful analysis to be clearly apprehended. (CP1-338)

The easiest of those which are of philosophical interest is the idea of a sign, or representation. A sign stands for something to the idea which it produces, or modifies. Or, it is a vehicle conveying into the mind something from without. That for which it stands is called its object; that which it conveys, its meaning; and the idea to which it gives rise, its interpretant. The object of representation can be nothing but a representation of which the first representation is the interpretant. But an endless series of representations, each representing the one behind it, may be conceived to have an absolute object at its limit. The meaning of a representation can be nothing but a representation. In fact, it is nothing but the representation itself conceived as stripped of irrelevant clothing. But this clothing never can be completely stripped off; it is only changed for something more diaphanous. So there is an infinite regression here. Finally, the interpretant is nothing but another representation to which the torch of truth is handed along; and as representation, it has its interpretant again. Lo, another infinite series. (CP1-339)

Some of the ideas of prominent Thirdness which, owing to their great importance in philosophy and in science, require attentive study are generality, infinity, continuity, diffusion, growth, and intelligence. (CP1-340)

The Reality of Thirdness
It is impossible to resolve everything in our thoughts into those two elements [of Firstness and Secondness]. We may say that the bulk of what is actually done consists of Secondness -- or better, Secondness is the predominant character of what has been done. The immediate present, could we seize it, would have no character but its Firstness. Not that I mean to say that immediate consciousness (a pure fiction, by the way), would be Firstness, but that the quality of what we are immediately conscious of, which is no fiction, is Firstness. But we constantly predict what is to be. Now what is to be, according to our conception of it, can never become wholly past. In general, we may say that meanings are inexhaustible. We are too apt to think that what one means to do and the meaning of a word are quite unrelated meanings of the word "meaning," or that they are only connected by both referring to some actual operation of the mind. Professor Royce especially in his great work The World and the Individual has done much to break up this mistake. In truth the only difference is that when a person means to do anything he is in some state in consequence of which the brute reactions between things will be moulded [in] to conformity to the form to which the man's mind is itself moulded, while the meaning of a word really lies in the way in which it might, in a proper position in a proposition believed, tend to mould the conduct of a person into conformity to that to which it is itself moulded. Not only will meaning always, more or less, in the long run, mould reactions to itself, but it is only in doing so that its own being consists. For this reason I call this element of the phenomenon or object of thought the element of Thirdness. It is that which is what it is by virtue of imparting a quality to reactions in the future. (CP1-343)

Three Modes of Being (Possibility, Actuality and Predictable Law)

My view is that there are three modes of being. I hold that we can directly observe them in elements of whatever is at any time before the mind in any way. They are the being of positive qualitative possibility, the being of actual fact, and the being of law that will govern facts in the future. (CP1-23)

Let us begin with considering actuality, and try to make out just what it consists in. If I ask you what the actuality of an event consists in, you will tell me that it consists in its happening then and there. The specifications then and there involve all its relations to other existents. The actuality of the event seems to lie in its relations to the universe of existents. A court may issue injunctions and judgments against me and I not care a snap of my finger for them. I may think them idle vapor. But when I feel the sheriff's hand on my shoulder, I shall begin to have a sense of actuality. Actuality is something brute. There is no reason in it. I instance putting your shoulder against a door and trying to force it open against an unseen, silent, and unknown resistance. We have a two-sided consciousness of effort and resistance, which seems to me to come tolerably near to a pure sense of actuality. On the whole, I think we have here a mode of being of one thing which consists in how a second object is. I call that Secondness. (CP1-24)

Besides this, there are two modes of being that I call Firstness and Thirdness. Firstness is the mode of being which consists in its subject's being positively such as it is regardless of aught else. That can only be a possibility. For as long as things do not act upon one another there is no sense or meaning in saying that they have any being, unless it be that they are such in themselves that they may perhaps come into relation with others. The mode of being a redness, before anything in the universe was yet red, was nevertheless a positive qualitative possibility. And redness in itself, even if it be embodied, is something positive and sui generis. That I call Firstness. We naturally attribute Firstness to outward objects, that is we suppose they have capacities in themselves which may or may not be already actualized, which may or may not ever be actualized, although we can know nothing of such possibilities [except] so far as they are actualized. (CP1-25)

Now for Thirdness. Five minutes of our waking life will hardly pass without our making some kind of prediction; and in the majority of cases these predictions are fulfilled in the event. Yet a prediction is essentially of a general nature, and cannot ever be completely fulfilled. To say that a prediction has a decided tendency to be fulfilled, is to say that the future events are in a measure really governed by a law. If a pair of dice turns up sixes five times running, that is a mere uniformity. The dice might happen fortuitously to turn up sixes a thousand times running. But that would not afford the slightest security for a prediction that they would turn up sixes the next time. If the prediction has a tendency to be fulfilled, it must be that future events have a tendency to conform to a general rule.
"Oh," but say the nominalists, "this general rule is nothing but a mere word or couple of words!" I reply, "Nobody ever dreamed of denying that what is general is of the nature of a general sign; but the question is whether future events will conform to it or not. If they will, your adjective 'mere' seems to be ill-placed." A rule to which future events have a tendency to conform is ipso facto an important thing, an important element in the happening of those events. This mode of being which consists, mind my word if you please, the mode of being which consists in the fact that future facts of Secondness will take on a determinate general character, I call a Thirdness. (CP1-26)

THE MONAD, THE DYAD, and THE TRIAD

THE MONAD:The pure idea of a monad is not that of an object. For an object is over against me. But it is much nearer an object than it is to a conception of self, which is still more complex. There must be some determination, or suchness, otherwise we shall think nothing at all. But it must not be an abstract suchness, for that has reference to a special suchness. It must be a special suchness with some degree of determination, not, however, thought as more or less. There is to be no comparison. So that it is a suchness sui generis. Imagine me to make and in a slumberous condition to have a vague, unobjectified, still less unsubjectified, sense of redness, or of salt taste, or of an ache, or of grief or joy, or of a prolonged musical note. That would be, as nearly as possible, a purely monadic state of feeling. Now in order to convert that psychological or logical conception into a metaphysical one, we must think of a metaphysical monad as a pure nature, or quality, in itself without parts or features, and without embodiment. Such is a pure monad. The meanings of names of "secondary" qualities are as good approximations to examples of monads as can be given. (CP1-303)

THE DYAD: A dyad consists of two subjects brought into oneness. These subjects have their modes of being in themselves, and they also have their modes of being, as first and second, etc., in connection with each other. They are two, if not really, at least in aspect. There is also some sort of union of them. The dyad is not the subjects; it has the subjects as one element of it. It has, besides, a suchness of monoidal character; and it has suchness, or suchnesses, peculiar to it as a dyad. The dyad brings the subjects together, and in doing so imparts a character to each of them. Those characters are, in some sense, two. The dyad has also two sides according to which subject is considered as first. These two sides of the dyad form a second pair of subjects attached to the dyad; and they have their mode of union. Each of them also has a special character as a subject of the dyad.
This description shows that the dyad, in contrast to the monad, has a variety of features; and all these features present dyadic relations. (CP1-326)

As an example of a dyad take this: God said, Let there be light, and there was light. We must not think of this as a verse of Genesis, for Genesis would be a third thing. Neither must we think of it as proposed for our acceptance, or as held for true; for we are third parties. We must simply think of God creating light by fiat. Not that the fiat and the coming into being of the light were two facts; but that it is in one indivisible fact. God and light are the subjects. The act of creation is to be regarded, not as any third object, but merely as the suchness of connection of God and light. The dyad is the fact. It determines the existence of the light, and the creatorship of God. The two aspects of the dyad are, first, that of God compelling the existence of the light, and that of the light as, by its coming into existence, making God a creator. This last is in the present example merely a mere point of view, without any reality corresponding to it. That is one of the special features of the particular example chosen. Of the two aspects of the dyad, then, one is in this instance, fundamental, real, and primary, while the other is merely derivative, formal, and secondary. (CP1-327)

I chose this instance because it is represented as instantaneous. Had there been any process intervening between the causal act and the effect, this would have been a medial, or third, element. Thirdness, in the sense of the category, is the same as mediation. For that reason, pure dyadism is an act of arbitrary will or of blind force; for if there is any reason, or law, governing it, that mediates between the two subjects and brings about their connection. The dyad is an individual fact, as it existentially is; and it has no generality in it. The being of a monadic quality is a mere potentiality, without existence. Existence is purely dyadic. (CP1-328)

It is to be noted that existence is an affair of blind force. "The very hyssop that grows on the wall exists in that chink because the whole universe could not prevent it." No law determines any atom to exist. Existence is presence in some experiential universe -- whether the universe of material things now existing, or that of laws, or that of phenomena, or that of feelings -- and this presence implies that each existing thing is in dynamical reaction with every other in that universe. Existence, therefore, is dyadic; though Being is monadic. (CP1-329)

THE TRIAD: I will sketch a proof that the idea of meaning is irreducible to those of quality and reaction. It depends on two main premisses. The first is that every genuine triadic relation involves meaning, as meaning is obviously a triadic relation. The second is that a triadic relation is inexpressible by means of dyadic relations alone. Considerable reflexion may be required to convince yourself of the first of these premisses, that every triadic relation involves meaning. There will be two lines of inquiry. First, all physical forces appear to subsist between pairs of particles. This was assumed by Helmholtz in his original paper, On the Conservation of Forces. Take any fact in physics of the triadic kind, by which I mean a fact which can only be defined by simultaneous reference to three things, and you will find there is ample evidence that it never was produced by the action of forces on mere dyadic conditions. Thus, your right hand is that hand which is toward the east, when you face the north with your head toward the zenith. Three things, east, west, and up, are required to define the difference between right and left. Consequently chemists find that those substances which rotate the plane of polarization to the right or left can only be produced from such [similar] active substances. They are all of such complex constitution that they cannot have existed when the earth was very hot, and how the first one was produced is a puzzle. It cannot have been by the action of brute forces. For the second branch of the inquiry, you must train yourself to the analysis of relations, beginning with such as are very markedly triadic, gradually going on to others. In that way, you will convince yourself thoroughly that every genuine triadic relation involves thought or meaning.
Take, for example, the relation of giving. A gives B to C. This does not consist in A's throwing B away and its accidentally hitting C, like the date-stone, which hit the Jinnee in the eye. If that were all, it would not be a genuine triadic relation, but merely one dyadic relation followed by another. There need be no motion of the thing given. Giving is a transfer of the right of property. Now right is a matter of law, and law is a matter of thought and meaning. I there leave the matter to your own reflection, merely adding that, though I have inserted the word "genuine," yet I do not really think that necessary. I think even degenerate triadic relations involve something like thought. (CP1-345)

And analysis will show that every relation which is tetradic, pentadic, or of any greater number of correlates is nothing but a compound of triadic relations. It is therefore not surprising to find that beyond the three elements of Firstness, Secondness, and Thirdness, there is nothing else to be found in the phenomenon. (CP1-347)

The triad in reasoning

It was Kant who first remarked the frequency in logical analytics of trichotomics or threefold distinctions.
Take any ordinary syllogism:
All men are mortal,
Elijah was a man;
Therefore, Elijah was mortal.
There are here three propositions, namely, two premisses and a conclusion; there are also three terms, man, mortal, and Elijah. If we transpose one of the premisses with the conclusion, denying both, we obtain what are called the indirect figures of syllogism; for example
All men are mortal,
But Elijah was not mortal;
Therefore, Elijah was not a man.

Elijah was not mortal,
But Elijah was a man;
Therefore, some men are not mortal.

Thus, there are three figures of ordinary syllogism. It is true there are other modes of inference which do not come under any of these heads; but that does not annul the fact that we have here a trichotomy.

The probable and approximate inferences of science must be classified on the very same principles, being either Deductions, Inductions, or Hypotheses.
Other examples of threes in logic are statements of what is actual, what is possible, and what is necessary; the three kinds of forms, Names, Propositions, and Inferences;. affirmative, negative, and uncertain answers to a question.
One very important triad is this: it has been found that there are three kinds of signs which are all indispensable in all reasoning; the first is the diagrammatic sign or icon, which exhibits a similarity or analogy to the subject of discourse; the second is the index, which like a pronoun demonstrative or relative, forces the attention to the particular object intended without describing it; the third [or symbol] is the general name or description which signifies its object by means of an association of ideas or habitual connection between the name and the character signified. (CP1-369)

The triad in reasoning
1. Three kinds of signs; as best shown in my last paper in the Am. Jour. Math.
2. Term, proposition, and argument, mentioned in my paper on a new list of categories.
3. Three kinds of argument, deduction, induction, hypothesis, as shown in my paper in Studies in Logic. Also three figures of syllogism, as shown there and in my paper on the Classification of Arguments.
4. Three kinds of terms, absolute, relative, and conjugative, as shown in my first paper on Logic of Relatives.
There are various other triads which may be alluded to.
The dual divisions of logic result from a false way of looking at things absolutely. Thus, besides affirmative and negative, there are really probable enunciations, which are intermediate. So besides universal and particular there are all sorts of propositions of numerical quantity.
For example, the particular proposition: Some A is B, means "At least one A is B." But we can also say: At least 2 A's are B's. Also, All the A's but one are B's, etc., etc., ad infinitum. We pass from dual quantity, or a system of quantity such as that of Boolian algebra, where there are only two values, to plural quantity. (CP1-354)

But there is one triad in particular which throws a strong light on the nature of all the others. Namely, we find it necessary to recognize in logic three kinds of characters, three kinds of facts. First there are singular characters which are predicable of single objects, as when we say that anything is white, large, etc. Secondly, there are dual characters which appertain to pairs of objects; these are implied by all relative terms as "lover," "similar," "other," etc. Thirdly, there are plural characters, which can all be reduced to triple characters but not to dual characters. Thus, we cannot express the fact that A is a benefactor of B by any descriptions of A and B separately; we must introduce a relative term. This is requisite, not merely in English, but in every language which might be invented. This is true even of such a fact as A is taller than B. If we say, "A is tall, but B is short," the conjugation "but" has a relative force, and if we omit this word the mere collocation of the two sentences is a relative or dual mode of signifying. . . . (CP1-370)

Let us now consider a triple character, say that A gives B to C. This is not a mere congeries of dual characters. It is not enough to say that A parts with C, and that B receives C. A synthesis of these two facts must be made to bring them into a single fact; we must express that C, in being parted with by A, is received by B. If, on the other hand, we take a quadruple fact, it is easy to express as a compound of two triple facts. . . . We are here able to express the synthesis of the two facts into one, because a triple character involves the conception of synthesis. Analysis involves the same relations as synthesis; so that we may explain the fact that all plural facts can be reduced to triple facts in this way.(CP1-371)

Peirce's Theory of Signs

Peirce’s theory of signs is a theory of language and reasoning, which holds that all modes of thinking depend on the use of signs.
According to Peirce, every thought is a sign, and every act of reasoning consists of the interpretation of signs.
Signs function as mediators between the external world of objects and the internal world of ideas. Signs may be mental representations of objects, and objects may be known by means of perception of their signs.
"Semiosis" is the process by which representations of objects function as signs. It is a process of cooperation between signs, their objects, and their "interpretants" (mental representations).
"Semiotic" (the science of signs) is the study of semiosis, and it is an inquiry into the conditions that are necessary in order for representations of objects to function as signs. Logic is described by Peirce as the science of the laws of signs.
(Alex Scott: Peirce’s Theory of Signs)

According to Peirce, the most important forms of thirdness involve meaning and representation, and all of his work is underpinned by a sophisticated theory of meaning: his semiotics. He probably believed that everything was a sign, but the signs of most interest to him were thoughts and ‘the assertions of a scientific intelligence’. This theory of meaning (‘speculative grammar’) was to provide foundations for his writings in logic.

The key to the thirdness involved in signs was Peirce’s notion of interpretation. A sign denotes an object only by being understood or interpreted as standing for an object: and this interpretation will always be another sign with the same object. Semiotics is thus primarily a theory of understanding, an account of how we are guided and constrained in arriving at interpretations of signs. Interpretation often involves inference, developing our understanding of the object in question.

Peirce was famous for his classifications of signs, and some of his terminology has acquired wide currency. For example, signs can be distinguished according to the features of them exploited in arriving at an interpretation.
A symbol denotes a particular object because there exists a practice of interpreting it as denoting that object.
An index denotes an object to which it stands in direct existential relation.
Iconic signs share some features with their object which each could possess if the other did not exist: Maps are straightforward examples, the conventions governing their use fixing how we are to interpret them as icons. Mathematical and logical symbolisms are iconic representations, and it was important for Peirce that sentences of natural languages have iconic elements too: formal inference exploits the fact that sentences exhibit a form which is shared with their subject-matter.
Much of Peirce’s later work attempted to use this systemic theory of meaning to provide a proof of pragmatist principle.

In conjunction with his Lowell Lectures, Peirce prepared a "Syllabus" to be distributed to his auditors. The first part is "An Outline Classification of the Sciences" (sel. 18), showing the normative sciences—esthetics, ethics, and logic—as constituting the central part of philosophy, and giving the order of epistemic and data—support relationships among the sciences that will guide his subsequent research. In "The Ethics of Terminology" (sel. 19), Peirce paused from his central task to elaborate on an issue that had been troubling him since he began working on logic entries in 1900 for Baldwin's Dictionary (and perhaps earlier with his work for the Century Dictionary): the unscientific terminology that prevailed in philosophy. Peirce recognized that philosophy could never abandon ordinary language altogether, for it is essential to understanding common conceptions, but philosophical analysis and progress calls for a specialized vocabulary. That was Peirce's strong conviction, and it explains his frequent resort to neologisms.

It may be that the attention Peirce gave to his classification of the sciences, along with his new-found conviction that logic is coextensive with semiotics, provided the impetus for the remaining two parts of the "Syllabus" that are included in EP2. They introduced a shift to an intensive development of his theory of signs along taxonomic lines motivated by his categories.
In "Sundry Logical Conceptions" (sel. 20), Peirce introduced the semiotic trichotomy that divides signs according to whether they are interpreted as signs of possibility, fact, or law: rhemes (here called sumisigns), dicisigns, and arguments.
That trichotomy was additional to his long-held division of signs according to whether they represent their objects by virtue of similarity, existential connection, or law: icons, indices, or symbols.
In "Nomenclature and Divisions of Triadic Relations" (sel. 21), Peirce introduced another trichotomy that distinguishes signs according to whether, in and of themselves, they are qualities, existents, or laws: qualisigns, sinsigns, and legisigns.
With these three trichotomies in place, Peirce was able to identify ten distinct classes of signs. This was the beginning of a rapid development of his formal semiotic theory. There were two other parts of the "Syllabus" that are not included in EP2, one on Peirce's system of Existential Graphs, which Peirce would later choose as the preferred medium for the presentation of his proof of pragmatism, and the other an in-depth treatment of dyadic relations parallel to the treatment of triadic relations found in selection 21.

In the next two selections Peirce shifted his attention from pragmatism and its proof to concentrate more fully on the theory of signs. In "New Elements" (sel. 22), he focused on the abstract mathematical structures necessarily exhibited by sign relations and argued, as he had in "On Science and Natural Classes," that "representations have power to cause real facts" and that "there can be no reality which has not the life of a symbol." And in "Ideas, Stray or Stolen, about Scientific Writing" (sel. 23) Peirce gave one of his most focused accounts of speculative rhetoric, the third branch of his semiotic trivium, which has as its aim to find out "the general secret of rendering signs effective." Peirce made it clear that the range of legitimate semiotic effects (interpretants) includes feelings and physical results, as well as thoughts and other signs. Peirce reiterated a point he had made at least as early as his Harvard Lectures, that nothing can be represented unless it is of the nature of a sign, and he stressed that ideas can only be communicated through their physical effects.

DIVISION OF SIGNS

§1. GROUND, OBJECT, AND INTERPRETANT
A sign, or representamen, is something which stands to somebody for something in some respect or capacity. It addresses somebody, that is, creates in the mind of that person an equivalent sign, or perhaps a more developed sign. That sign which it creates I call the interpretant of the first sign.
The sign stands for something, its object. It stands for that object, not in all respects, but in reference to a sort of idea, which I have sometimes called the ground of the representamen. (Condensed CP2-228)

Every representamen is thus connected with three things, the ground, the object, and the interpretant. (Condensed CP2-229)

§2. SIGNS AND THEIR OBJECTS
The word Sign will be used to denote an Object perceptible, or only imaginable, or even unimaginable in one sense--for the word "fast," which is a Sign, is not imaginable, since it is not this word itself that can be set down on paper or pronounced, but only an instance of it, and since it is the very same word when it is written as it is when it is pronounced, but is one word when it means "rapidly" and quite another when it means "immovable," and a third when it refers to abstinence.
But in order that anything should be a Sign, it must "represent," as we say, something else, called its Object. (Condensed CP2-230)

§3. DIVISION OF TRIADIC RELATIONS

In the case of triadic relations, no part of this work has, as yet, been satisfactorily performed, except in some measure for the most important class of triadic relations, those of signs, or representamens, to their objects and interpretants. (CP2-233)

Provisionally, we may make a rude division of triadic relations into-Triadic relations of comparison, Triadic relations of performance, and Triadic relations of thought.
Triadic relations of Comparison are those which are of the nature of logical possibilities.
Triadic relations of Performance are those which are of the nature of actual facts.
Triadic relations of Thought are those which are of the nature of a law.
(CP2-234)

A Representamen is the First Correlate of a triadic relation, the Second Correlate being termed its Object, and the possible Third Correlate being termed its Interpretant, by which triadic relation the possible Interpretant is determined to be the First Correlate of the same triadic relation to the same Object, and for some possible Interpretant. (CP2-242)

A Sign is a representamen of which some interpretant is a cognition of a mind.
Signs are the only representamens that have been much studied. (CP2-242)

Signs are divisible by three trichotomies: FIRST - according as the sign in itself is a mere quality, is an actual existent, or is a general law; SECOND -according as the relation of the sign to its object consists in the sign's having some character in itself, or in some existential relation to that object, or in its relation to an interpretant; THIRD -according as its Interpretant represents it as a sign of possibility or as a sign of fact or a sign of reason. (Condensed CP2-243)

§4. FIRST TRICHOTOMY OF SIGNS - according as the sign in itself is a mere quality, is an actual existent, or is a general law: 1)a Qualisign, 2) a Sinsign, or 3) a Legisign.

1) A Qualisign is a quality which is a Sign. It cannot actually act as a sign until it is embodied; but the embodiment has nothing to do with its character as a sign. (CP2-244)

2) A Sinsign (where the syllable sin is taken as meaning "being only once," as in single, simple.) is an actual existent thing or event which is a sign. It can only be so through its qualities; so that it involves a qualisign, or rather, several qualisigns. But these qualisigns are of a peculiar kind and only form a sign through being actually embodied. (CP2-245)

3) A Legisign is a law that is a Sign. This law is usually established by men. Every conventional sign is a legisign [but not conversely]. It is not a single object, but a general type which, it has been agreed, shall be significant. Every legisign signifies through an instance of its application, which may be termed a Replica of it. Thus, the word "the" will usually occur from fifteen to twenty-five times on a page. It is in all these occurrences one and the same word, the same legisign. Each single instance of it is a Replica. The Replica is a Sinsign. Thus, every Legisign requires Sinsigns. But these are not ordinary Sinsigns, such as are peculiar occurrences that are regarded as significant. Nor would the Replica be significant if it were not for the law which renders it so. (CP2-246)

§5. SECOND TRICHOTOMY OF SIGNS -according as the relation of the sign to its object consists 1) in the sign's having some character in itself, or 2) in some existential relation to that object, or 3) in its relation to an interpretant; A Sign may be termed 1) an Icon, 2) an Index, or3) a Symbol

1) An Icon is a sign which refers to the Object that it denotes merely by virtue of characters of its own, and which it possesses, just the same, whether any such Object actually exists or not. It is true that unless there really is such an Object, the Icon does not act as a sign; but this has nothing to do with its character as a sign. Anything whatever, be it quality, existent individual, or law, is an Icon of anything, in so far as it is like that thing and used as a sign of it. (CP2-247)

2) An Index is a sign which refers to the Object that it denotes by virtue of being really affected by that Object. It cannot, therefore, be a Qualisign, because qualities are whatever they are independently of anything else. In so far as the Index is affected by the Object, it necessarily has some Quality in common with the Object, and it is in respect to these that it refers to the Object. It does, therefore, involve a sort of Icon, although an Icon of a peculiar kind; and it is not the mere resemblance of its Object, even in these respects which makes it a sign, but it is the actual modification of it by the Object. the mere resemblance of its Object, even in these respects which makes it a sign, but it is the actual modification of it by the Object. (CP2-248)

3) A Symbol is a sign which refers to the Object that it denotes by virtue of a law, usually an association of general ideas, which operates to cause the Symbol to be interpreted as referring to that Object. It is thus itself a general type or law, that is, is a Legisign. As such it acts through a Replica. Not only is it general itself, but the Object to which it refers is of a general nature. Now that which is general has its being in the instances which it will determine. There must, therefore, be existent instances of what the Symbol denotes, although we must here understand by "existent," existent in the possibly imaginary universe to which the Symbol refers. The Symbol will indirectly, through the association or other law, be affected by those instances; and thus the Symbol will involve a sort of Index, although an Index of a peculiar kind. It will not, however, be by any means true that the slight effect upon the Symbol of those instances accounts for the significant character of the Symbol. (CP2-249)

§6. THIRD TRICHOTOMY OF SIGNS - according as its Interpretant represents it as a sign of possibility or as a sign of fact or as a sign of reason.
A Sign may be termed 1) a Rheme, 2) a Dicisign or a Dicent Sign (that is, a proposition or quasi-proposition), or 3) an Argument. (CP2-250)
(Note: A rheme is interpreted as a sign of possibility, a dicisign (or "dicent sign") is interpreted as a sign of actual existence, and an argument is interpreted as a sign of a law (or of a necessary truth).

2) A Dicent Sign is a Sign, which, for its Interpretant, is a Sign of actual existence. It cannot, therefore, be an Icon, which affords no ground for an interpretation of it as referring to actual existence.
1) Rheme is essential to the Dicisign, it by no means constitutes it. A Dicisign necessarily involves, as a part of it, a Rheme, to describe the fact which it is interpreted as indicating.
3) An Argument is a Sign which, for its Interpretant, is a Sign of law. (CP2-251-252)

1) A Rheme is a sign which is understood to represent its object in its characters merely; that 2) a Dicisign is a sign which is understood to represent its object in respect to actual existence; and that 3) an Argument is a Sign which is understood to represent its Object in its character as Sign. (CP2-252)

What is the essence of a Judgment?
A judgment is the mental act by which the judger seeks to impress upon himself the truth of a proposition. It is much the same as an act of asserting the proposition, or going before a notary and assuming formal responsibility for its truth, except that those acts are intended to affect others, while the judgment is only intended to affect oneself.
However, the logician, as such, cares not what the psychological nature of the act of judging may be. The question for him is: What is the nature of the sort of sign of which a principal variety is called a proposition, which is the matter upon which the act of judging is exercised?
The proposition need not be asserted or judged. It may be contemplated as a sign capable of being asserted or denied. This sign itself retains its full meaning whether it be actually asserted or not. The peculiarity of it, therefore, lies in its mode of meaning; and to say this is to say that its peculiarity lies in its relation to its interpretant.
The proposition professes to be really affected by the actual existent or real law to which it refers. The argument makes the same pretension, but that is not the principal pretension of the argument. The rheme makes no such pretension. (CP2-252)

The Interpretant of the Argument represents it as an instance of a general class of Arguments, which class on the whole will always tend to the truth. It is this law, in some shape, which the argument urges; and this "urging" is the mode of representation proper to Arguments.
The Argument must, therefore, be a Symbol, or Sign whose Object is a General Law or Type.
It must involve a Dicent Symbol, or Proposition, which is termed its Premiss; for the Argument can only urge the law by urging it in an instance. (CP2-253)

§7. TEN CLASSES OF SIGNS
The three trichotomies of Signs result together in dividing Signs into TEN CLASSES OF SIGNS, of which numerous subdivisions have to be considered. (CP2 -254-263)

Ten classes of signs, according to Peirce, are produced by triads of simple signs. Each of the ten classes of signs corresponds to a distinct triadic relation between the categories of firstness, secondness, and thirdness. Thus, the classification table shows that: (1) "qualisigns" correspond to the relation of firstness-firstness-firstness, (2) "iconic sinsigns" correpond to the relation of firstness-firstness-secondness, (3) "rhematic indexical sinsigns" correspond to the relation of firstness-secondness-secondness, (4) "dicent sinsigns" correspond to the relation of secondness-secondness-secondness, (5) "iconic legisigns" correspond to the relation of firstness-firstness-thirdness, (6) "rhematic indexical legisigns" correspond to the relation of firstness-secondness-thirdness, " (7) "dicent indexical legisigns" correspond to the relation of secondness-secondness-thirdness, (8) "rhematic symbols" correspond to the relation of firstness-thirdness-thirdness, (9) "dicent symbols" correspond to the relation of secondness-thirdness-thirdness, and (10) "arguments" correspond to the relation of thirdness-thirdness-thirdness. (Alex Scott: Peirce’s Theory of Signs)

§9. THE TRICHOTOMY OF ARGUMENTS
An Argument is always understood by its Interpretant to belong to a general class of analogous arguments, which class, as a whole, tends toward the truth. This may happen in three ways, giving rise to a trichotomy of all simple arguments into Deductions, Inductions, and Abductions. (Condensed CP2-266)

Firstness, Secondness, and Thirdness

A sign is something that evokes something in some respect for someone. The sign stands for an object and, at the same time, it creates in the mind of that person another sign (called the “interpretant”) that interprets and translates the original sign into a meaningful idea.

Firstness is a condition of unmediated, unreflexive experience. It is an action without reaction, cause without effect, and sensation without perception. It is a possibility but not yet an event.
Secondness is a condition of mediated but not reflexive experience. It is an action and the reaction it evokes, cause and the effect, but not yet reflection on the experience. It is a perception but not a conceptual idea. It is an actual event but unreflective.
Thirdness is a condition of mediated, reflexive experience. It is an action and reaction, cause and effect, and the reflection of that experience resulting in the formation of habit or conceptual law.

Peirce’s semiotic follows this triadic structure. The sign is the first, the object it evokes is the second, and the interpretant which mediates the meaning of sign-object relation is the third.

Where signs are concerned, they are characterized by:
I. their presentative condition (the ground, or the quality that makes them a sign), a condition of firstness;
II. their representative condition (the relation in which they stand to their object), a condition of secondness;
III. their interpretative power (their ability to direct attention to an object in such a way as to evoke an interpretant), a condition of thirdness.

Each of these conditions is also follows a triadic structure.

I. Peirce identifies three types of signs as a function of their presentative condition.
Firstness: qualisigns, or qualities that act as signs (the color red),
Secondness: sinsigns, or actual instantiations of signs (a light that turns red), and
Thirdness: legisigns, or signs that have a meaning deriving from convention, habit, or law (a red traffic light that signals to drivers to stop).

II. He also identifies three types of signs as a function of their representative condition.
Firstness: icons, or signs that resemble their object (an image of fire),
Secondness: indices, or signs that are contiguous with, are caused by, or somehow point to their objects (smoke coming from a fire), and
Thirdness: symbols, or signs whose meanings are a function of convention, habit, or law (fire as knowledge in the story of Prometheus).

III. The same is true of signs as a function of their interpretive condition.
Firstness: rhemes identify a sign but do not reveal whether it exists or can be judged true or false (“a dog”),
Secondness: dicents are propositions that can be judged true or false (“a dog is an animal”), and
Thirdness: arguments are signs whose interpretation relates to convention, habit, or law (“a dog is a man’s best friend”).

One implication of these typologies is that we can identify ten types of signs ranging from the barely elaborated (rhematic iconic qualisigns such as “a nebulous patch of color, seeing a blotch of red in an afterimage, hearing the wind blow through an old house, the musty smell while walking in a forest, the aftertaste from a deliciously exotic meal”) to the complex (argumentative symbolic legisigns, where the “paradigm case is that of an inference of an argument, which shows the connection between one set of propositions [the premises] and another [the conclusion]”.

Why only ten types, rather than twenty-seven, as three sets of triads would suggest? Peirce argues the interpretive condition of a sign cannot be of a higher order than its representative condition, which in turn cannot be of a higher order than its presentative condition. That is, a qualisign (a first) cannot be a dicent (a second) or an argument (a third), nor can it be an index (a second) or a symbol (a third). As a result, the only type of qualisign conceivable is a rhematic iconic qualisign, but many types of legisigns are conceivable.

Peirce's Theory of Signs

The development of genuine thirdness, or Representation is by an elaborate process founded upon experience and reason combined.
There are three subclasses or genera of Thirdness:
1. a relatively qualitative thirdness or thirdness of the last degeneracy.
2. a relatively reactional thirdness or thirdness of the lesser degree of degeneracy,
3. a relatively genuine thirdness,

1. This last last degeneracy, the qualitatively degenerate genus, may subdivide, and its species may even be governed by the three categories, but it will not subdivide, in the manner which we are considering, by the essential determinations of its conception.
2. The genus corresponding to the lesser degree of degeneracy, the reactionally degenerate genus, will subdivide after the manner of the Second category, forming a catena.
3. The genus of relatively genuine Thirdness will subdivide by Trichotomy just like that from which it resulted. Only as the division proceeds, the subdivisions become harder and harder to discern.

Of these three genera of representamens, the Icon is the Qualitatively degenerate, the Index the Reactionally degenerate, while the Symbol is the relatively genuine genus.
(Reference: CP 5-72)

The most degenerate Thirdness is where we conceive a mere Quality of Feeling, or Firstness, to represent itself to itself as Representation. Such, for example, would be Pure Self-Consciousness, which might be roughly described as a mere feeling that has a dark instinct of being a germ of thought.(CP 5-71)

The representamen, for example, divides by trichotomy into the general sign or symbol, the index, and the icon.
1. An icon is a representamen which fulfills the function of a representamen by virtue of a character which it possesses in itself, and would possess just the same though its object did not exist. Thus, the statue of a centaur is not, it is true, a representamen if there be no such thing as a centaur. Still, if it represents a centaur, it is by virtue of its shape; and this shape it will have, just as much, whether there be a centaur or not.
2. An index is a representamen which fulfills the function of a representamen by virtue of a character which it could not have if its object did not exist, but which it will continue to have just the same whether it be interpreted as a representamen or not. For instance, an old-fashioned hygrometer is an index. For it is so contrived as to have a physical reaction with dryness and moisture in the air, so that the little man will come out if it is wet, and this would happen just the same if the use of the instrument should be entirely forgotten, so that it ceased actually to convey any information.
3. A symbol is a representamen which fulfills its function regardless of any similarity or analogy with its object and equally regardless of any factual connection therewith, but solely and simply because it will be interpreted to be a representamen. Such for example is any general word, sentence, or book.
(CP 5-73)

What Is a Sign?

MS 404. [Published in part in CP 2.281, 285, and 297-302. This work, probably composed early in 1894, was originally the first chapter of a book entitled "The Art of Reasoning," but was then turned into the second chapter of Peirce's multi-volume "How to Reason: A Critick of Arguments" (also known as "Grand Logic").] In this selection Peirce gives an account of signs based on an analysis of conscious experience from the standpoint of his three universal categories. He discusses the three principal kinds of signs—icons, indices, and symbols—and provides many examples. He maintains, as he had earlier, that reasoning must involve all three kinds of signs, and he claims that the art of reasoning is the art of marshalling signs, thus emphasizing the relationship between logic and semiotics.

§1. This is a most necessary question, since all reasoning is an interpretation of signs of some kind. But it is also a very difficult question, calling for deep reflection.

It is necessary to recognize three different states of mind. First, imagine a person in a dreamy state. Let us suppose he is thinking of nothing but a red color. Not thinking about it, either, that is, not asking nor answering any questions about it, not even saying to himself that it pleases him, but just contemplating it, as his fancy brings it up. Perhaps, when he gets tired of the red, he will change it to some other color,—say a turquoise blue,—or a rose-color;—but if he does so, it will be in the play of fancy without any reason and without any compulsion. This is about as near as may be to a state of mind in which something is present, without compulsion and without reason; it is called Feeling. Except in a half-waking hour, nobody really is in a state of feeling, pure and simple. But whenever we are awake, something is present to the mind, and what is present, without reference to any compulsion or reason, is feeling.

Second, imagine our dreamer suddenly to hear a loud and prolonged steam whistle. At the instant it begins, he is startled. He instinctively tries to get away; his hands go to his ears. It is not so much that it is unpleasing, but it forces itself so upon him. The instinctive resistance is a necessary part of it: the man would not be sensible his will was borne down, if he had no self-assertion to be borne down. It is the same when we exert ourselves against outer resistance; except for that resistance we should not have anything upon which to exercise strength. This sense of acting and of being acted upon, which is our sense of the reality of things,—both of outward things and of ourselves,—may be called the sense of Reaction. It does not reside in any one Feeling; it comes upon the breaking of one feeling by another feeling. It essentially involves two things acting upon one another

. Third, let us imagine that our now-awakened dreamer, unable to shut out the piercing sound, jumps up and seeks to make his escape by the door, which we will suppose had been blown to with a bang just as the whistle commenced. But the instant our man opens the door let us say the whistle ceases. Much relieved, he thinks he will return to his seat, and so shuts the door, again. No sooner, however, has he done so than the whistle recommences. He asks himself whether the shutting of the door had anything to do with it; and once more opens the mysterious portal. As he opens it, the sound ceases. He is now in a third state of mind: he is Thinking. That is, he is aware of learning, or of going through a process by which a phenomenon is found to be governed by a rule, or has a general knowable way of behaving. He finds that one action is the means, or middle, for bringing about another result. This third state of mind is entirely different from the other two. In the second there was only a sense of brute force; now there is a sense of government by a general rule. In Reaction only two things are involved; but in government there is a third thing which is a means to an end. The very word means signifies something which is in the middle between two others. Moreover, this third state of mind, or Thought, is a sense of learning, and learning is the means by which we pass from ignorance to knowledge. As the most rudimentary sense of Reaction involves two states of Feeling, so it will be found that the most rudimentary Thought involves three states of Feeling.

As we advance into the subject, these ideas, which seem hazy at our first glimpse of them, will come to stand out more and more distinctly; and their great importance will also force itself upon our minds.

§2. There are three kinds of interest we may take in a thing. First, we may have a primary interest in it for itself. Second, we may have a secondary interest in it, on account of its reactions with other things. Third, we may have a mediatory interest in it, in so far as it conveys to a mind an idea about a thing. In so far as it does this, it is a sign, or representation.

§3. There are three kinds of signs. Firstly, there are likenesses, or icons; which serve to convey ideas of the things they represent simply by imitating them. Secondly, there are indications, or indices; which show something about things, on account of their being physically connected with them. Such is a guidepost, which points down the road to be taken, or a relative pronoun, which is placed just after the name of the thing intended to be denoted, or a vocative exclamation, as "Hi! there," which acts upon the nerves of the person addressed and forces his attention. Thirdly, there are symbols, or general signs, which have become associated with their meanings by usage. Such are most words, and phrases, and speeches, and books, and libraries.

Let us consider the various uses of these three kinds of signs more closely.

§4. Likenesses. Photographs, especially instantaneous photographs, are very instructive, because we know that they are in certain respects exactly like the objects they represent. But this resemblance is due to the photographs having been produced under such circumstances that they were physically forced to correspond point by point to nature. In that aspect, then, they belong to the second class of signs, those by physical connection. The case is different, if I surmise that zebras are likely to be obstinate, or otherwise disagreeable animals, because they seem to have a general resemblance to donkeys, and donkeys are self-willed. Here the donkey serves precisely as a probable likeness of the zebra. It is true we suppose that resemblance has a physical cause in heredity; but then, this hereditary affinity is itself only an inference from the likeness between the two animals, and we have not (as in the case of the photograph) any independent knowledge of the circumstances of the production of the two species. Another example of the use of a likeness is the design an artist draws of a statue, pictorial composition, architectural elevation, or piece of decoration, by the contemplation of which he can ascertain whether what he proposes will be beautiful and satisfactory. The question asked is thus answered almost with certainty because it relates to how the artist will himself be affected. The reasoning of mathematicians will be found to turn chiefly upon the use of likenesses, which are the very hinges of the gates of their science. The utility of likenesses to mathematicians consists in their suggesting, in a very precise way, new aspects of supposed states of things. For example, suppose we have a winding curve, with continual points where the curvature changes from clockwise to counter-clockwise and conversely as in figure 1. Let us further suppose that this curve is continued so that it crosses itself at every such point of reversed bending in another such point. The result appears in figure 2. It may be described as a number of ovals flattened together, as if by pressure. One would not perceive that the first description and the second were equivalent, without the figures. We shall find, when we get further into the subject, that all these different uses of likeness may be brought under one general formula.

In intercommunication, too, likenesses are quite indispensable. Imagine two men who know no common speech, thrown together remote from the rest of the race. They must communicate; but how are they to do so? By imitative sounds, by imitative gestures, and by pictures. These are three kinds of likenesses. It is true that they will also use other signs, finger-pointings, and the like. But, after all, the likenesses will be the only means of describing the qualities of the things and actions which they have in mind. Rudimentary language, when men first began to talk together, must have largely consisted either in directly imitative words, or in conventional names which they attached to pictures. The Egyptian language is an excessively rude one. It was, as far as we know, the earliest to be written; and the writing is all in pictures. Some of these pictures came to stand for sounds,—letters and syllables. But others stand directly for ideas. They are not nouns; they are not verbs; they are just pictorial ideas.

§5. Indications. But pictures alone,—pure likenesses,—can never convey the slightest information. Thus, figure 3 suggests a wheel. But it leaves the spectator uncertain whether it is a copy of something actually existing or a mere play of fancy. The same thing is true of general language and of all symbols. No combination of words (excluding proper nouns, and in the absence of gestures or other indicative concomitants of speech) can ever convey the slightest information. This may sound paradoxical; but the following imaginary little dialogue will show how true it is:

Two men, A and B, meet on a country road, when the following conversation ensues.
B. The owner of that house is the richest man in these parts.
A. What house?
B. Why do you not see a house to your right about seven kilometres distant, on a hill?
A. Yes, I think I can descry it.
B. Very well; that is the house.

Thus, A has acquired information. But if he walks to a distant village and says "the owner of a house is the richest man in those parts," the remark will refer to nothing, unless he explains to his interlocutor how to proceed from where he is in order to find that district and that house. Without that, he does not indicate what he is talking about. To identify an object, we generally state its place at a stated time; and in every case must show how an experience of it can be connected with the previous experience of the hearer. To state a time, we must reckon from a known epoch,—either the present moment, or the assumed birth of Christ, or something of the sort. When we say the epoch must be known, we mean it must be connected with the hearer's experience. We also have to reckon in units of time; and there is no way of making known what unit we propose to use except by appealing to the hearer's experience. So no place can be described, except relatively to some known place; and the unit of distance used must be defined by reference to some bar or other object which people can actually use directly or indirectly in measurement. It is true that a map is very useful in designating a place; and a map is a sort of picture. But unless the map carries a mark of a known locality, and the scale of miles, and the points of the compass, it no more shows where a place is than the map in Gulliver's Travels shows the location of Brobdingnag. It is true that if a new island were found, say, in the Arctic Seas, its location could be approximately shown on a map which should have no lettering, meridians, nor parallels; for the familiar outlines of Iceland, Nova Zemla, Greenland, etc., serve to indicate the position. In such a case, we should avail ourselves of our knowledge that there is no second place that any being on this earth is likely to make a map of which has outlines like those of the Arctic shores. This experience of the world we live in renders the map something more than a mere icon and confers upon it the added characters of an index. Thus, it is true that one and the same sign may be at once a likeness and an indication. Still, the offices of these orders of signs are totally different. It may be objected that likenesses as much as indices are founded on experience, that an image of red is meaningless to the color blind, as is that of erotic passion to the child. But these are truly objections which help the distinction; for it is not experience, but the capacity for experience, which they show is requisite for a likeness; and this is requisite, not in order that the likeness should be interpreted, but in order that it should at all be presented to the sense. Very different is the case of the inexperienced and the experienced person meeting the same man and noticing the same peculiarities, which to the experienced man indicate a whole history, but to the inexperienced reveal nothing.

Let us examine some examples of indications. I see a man with a rolling gait. This is a probable indication that he is a sailor. I see a bowlegged man in corduroys, gaiters, and a jacket. These are probable indications that he is a jockey or something of the sort. A weathercock indicates the direction of the wind. A sun-dial or a clock indicates the time of day. Geometricians mark letters against the different parts of their diagrams and then use those letters to indicate those parts. Letters are similarly used by lawyers and others. Thus, we may say: If A and B are married to one another and C is their child while D is brother of A, then D is uncle of C. Here A, B, C, and D fulfill the office of relative pronouns, but are more convenient since they require no special collocation of words. A rap on the door is an indication. Anything which focuses the attention is an indication. Anything which startles us is an indication, in so far as it marks the junction between two portions of experience. Thus a tremendous thunderbolt indicates that something considerable happened, though we may not know precisely what the event was. But it may be expected to connect itself with some other experience.

§6. Symbols. The word symbol has so many meanings that it would be an injury to the language to add a new one. I do not think that the signification I attach to it, that of a conventional sign, or one depending upon habit (acquired or inborn), is so much a new meaning as a return to the original meaning. Etymologically, it should mean a thing thrown together, just as embolon (embolum) is a thing thrown into something, a bolt, and parabolon (parabolum) is a thing thrown besides, collateral security, and upobolon (hypobolum) is a thing thrown underneath, an antenuptial gift. It is usually said that in the word symbol, the throwing together is to be understood in the sense of to conjecture; but were that the case, we ought to find that sometimes, at least, it meant a conjecture, a meaning for which literature may be searched in vain. But the Greeks used "throw together" (sumballein) very frequently to signify the making of a contract or convention. Now, we do find symbol (sumbolon) early and often used to mean a convention or contract. Aristotle calls a noun a "symbol," that is, a conventional sign. In Greek, a watch-fire is a "symbol," that is, a signal agreed upon; a standard or ensign is a "symbol," a watch-word is a "symbol," a badge is a "symbol"; a church creed is called a symbol, because it serves as a badge or shibboleth; a theatre-ticket is called a "symbol"; any ticket or check entitling one to receive anything is a "symbol." Moreover, any expression of sentiment was called a "symbol." Such were the principal meanings of the word in the original language. The reader will judge whether they suffice to establish my claim that I am not seriously wrenching the word in employing it as I propose to do.

Any ordinary word, as "give," "bird," "marriage," is an example of a symbol. It is applicable to whatever may be found to realize the idea connected with the word; it does not, in itself, identify those things. It does not show us a bird, nor enact before our eyes a giving or a marriage, but supposes that we are able to imagine those things, and have associated the word with them.

§7. A regular progression of one, two, three may be remarked in the three orders of signs, Likeness, Index, Symbol. The likeness has no dynamical connection with the object it represents; it simply happens that its qualities resemble those of that object, and excite analogous sensations in the mind for which it is a likeness. But it really stands unconnected with them. The index is physically connected with its object; they make an organic pair. But the interpreting mind has nothing to do with this connection, except remarking it, after it is established. The symbol is connected with its object by virtue of the idea of the symbol-using mind, without which no such connection would exist.

Every physical force reacts between a pair of particles, either of which may serve as an index of the other. On the other hand, we shall find that every intellectual operation involves a triad of symbols.

§8. A symbol, as we have seen, cannot indicate any particular thing; it denotes a kind of thing. Not only that, but it is itself a kind and not a single thing. You can write down the word "star"; but that does not make you the creator of the word, nor if you erase it have you destroyed the word. The word lives in the minds of those who use it. Even if they are all asleep, it exists in their memory. So we may admit, if there be reason to do so, that generals are mere words without at all saying, as Ockham supposed, that they are really individuals.

Symbols grow. They come into being by development out of other signs, particularly from likenesses or from mixed signs partaking of the nature of likenesses and symbols. We think only in signs. These mental signs are of mixed nature; the symbol-parts of them are called concepts. If a man makes a new symbol, it is by thoughts involving concepts. So it is only out of symbols that a new symbol can grow. Omne symbolum de symbolo. A symbol, once in being, spreads among the peoples. In use and in experience, its meaning grows. Such words as force, law, wealth, marriage, bear for us very different meanings from those they bore to our barbarous ancestors. The symbol may, with Emerson's sphynx, say to man,

Of thine eye I am eyebeam.

§9. In all reasoning, we have to use a mixture of likenesses, indices, and symbols. We cannot dispense with any of them. The complex whole may be called a symbol; for its symbolic, living character is the prevailing one. A metaphor is not always to be despised: though a man may be said to be composed of living tissues, yet portions of his nails, teeth, hair, and bones, which are most necessary to him, have ceased to undergo the metabolic processes which constitute life, and there are liquids in his body which are not alive. Now, we may liken the indices we use in reasoning to the hard parts of the body, and the likenesses we use to the blood: the one holds us stiffly up to the realities, the other with its swift changes supplies the nutriment for the main body of thought.

Suppose a man to reason as follows: The Bible says that Enoch and Elijah were caught up into heaven; then, either the Bible errs, or else it is not strictly true that all men are mortal. What the Bible is, and what the historic world of men is, to which this reasoning relates, must be shown by indices. The reasoner makes some sort of mental diagram by which he sees that his alternative conclusion must be true, if the premise is so; and this diagram is an icon or likeness. The rest is symbols; and the whole may be considered as a modified symbol. It is not a dead thing, but carries the mind from one point to another. The art of reasoning is the art of marshalling such signs, and of finding out the truth.

Peirce’s pragmatism

Peirce’s Early Pragmatism (Nominalism)

Peirce’s Later Pragmaticism (Realism)

Peirce’s Later Pragmaticism (Realism)

Theory of Inquiry - Cognition - Epistemology

On a New List of Categories

Questions Concerning Certain Faculties Claimed for Man

Some Consequences of Four Incapacities

Peirce's Later Years -The 1903 Harvard Lectures

Peirce's Architectonic Structure of Philosophy

Peirce's Architectonic Structure

What Is Peirce’s Architectonic View Of Science?

Pragmatism’s Efficacy versus Pragmatism’s Truth

The Role of Pragmatism in Logic and the Role of Logic in the Architectonic of Science

Phenomenology (Phaneroscopy)

Peirce's Three Phenomenological Categories

Aesthetics and ethics

What Are Peirce's Three Phenomenological Categories?

"Trichotomy"

"Peirce's Trichotomy"

Firstness, Secondness and Thirdness

FIRSTNESS

SECONDNESS

THIRDNESS

Three Modes of Being (Possibility, Actuality and Predictable Law)

THE MONAD, THE DYAD, and THE TRIAD

The triad in reasoning

Semiotic and Logic

DIVISION OF SIGNS

Firstness, Secondness, and Thirdness

Peirce's Theory of Signs

What Is a Sign?

Abduction

The Logic of Abduction

Perception and Perceptual Judgment

Perceptual Judgment

Perceptual Judgment and Abduction

Issues of Pragmatism

A SURVEY OF PRAGMATICISM

"Peirce's Theory of Sign"

"Peirce's Trichotomy"

"It is easy to be certain"

"The public prefer the cheap and nasty."

"Pragmatism Theory of Mind"

"Pragmatism = Logical Psychology"