Rudolf Carnap (1891 – 1970) German-born American philosopher of logical positivism. He made important contributions to logic, the analysis of language, the theory of probability, and the philosophy of science.
(Encyclopædia Britannica)

Rudolf Carnap was an influential philosopher who was active in central Europe before 1935 and in the United States thereafter. He was a leading member of the Vienna Circle and probably the most important advocate for logical positivism and the program of the Vienna Circle, at least in the United States. Carnap wrote an enormous amount, and he (and Carl Hempel) did more to work out the details of the logical positivist program and thereby promote that program in America and elsewhere than anyone else.

Carnap's work and method were strongly characterized by an emphasis on clarity, and a conviction that clarity is achieved through expressing things in symbolic form. He himself wrote that from an early age:
"I began to apply symbolic notation, now more frequently in the Principia form than in Frege's, in my own thinking about philosophical problems or in the formulation of axiom systems. When I considered a concept or a proposition occurring in a scientific or philosophical discussion, I thought I understood it clearly only if I felt that I could express it, if I wanted to, in symbolic language." (Qtd. in Schilpp 1984, 11)
(New World Encyclopedia)

"The function of logical analysis is to analyse all knowledge, all assertions of science and of everyday life, in order to make clear the sense of each such assertion and the connections between them. One of the principal tasks of the logical analysis of a given proposition is to find out the method of verification for that proposition." — Carnap's Philosophy and Logical Syntax, pp 9-10.

In 1934 he wrote Logical Syntax of Language that was to make him the most famous logical positivist and member of the Vienna Circle. In this work, Carnap advanced his Principle of Tolerance, according to which there is not any such thing as a "true" or "correct" logic or language. One is free to adopt whatever form of language is useful for one's purposes.

Philosophy is to be replaced by the logic of science – that is to say, by the logical analysis of the concepts and sentences of the sciences, for the logic of science is nothing other than the logical syntax of the language of science. — Carnap's Logical Syntax of Language, Foreword.

According to this view, the sentences of metaphysics are pseudo-sentences which on logical analysis are proved to be either empty phrases or phrases which violate the rules of syntax. Of the so-called philosophical problems, the only questions which have any meaning are those of the logic of science. To share this view is to substitute logical syntax for philosophy. — Carnap's Logical Syntax of Language, p 8.
(Wikipedia)

Since his Vienna years, Carnap had been much concerned also with problems in logic and in the philosophy of language. He held that philosophical perplexities often arise from a misunderstanding or misuse of language and that the way to resolve them is by “logical analysis of language.” On this point, he agreed with the “ordinary language” school of analytic philosophy, which had its origins in England. He differed from it, however, in insisting that more technical issues—e.g., those in the philosophy of science or of mathematics—cannot be adequately dealt with by considerations of ordinary linguistic usage but require clarification by reference to artificially constructed languages that are formulated in logical symbolism and that have their structure and interpretation precisely specified by so-called syntactic and semantic rules. Carnap developed these ideas and the theoretical apparatus for their implementation in a series of works, including Logische Syntax der Sprache (1934; The Logical Syntax of Language) and Meaning and Necessity (1947). Carnap’s interest in artificial languages included advocacy of international auxiliary languages such as Esperanto and Interlingua to facilitate scholarly communication and to further international understanding.

From about 1945 onward, Carnap turned his efforts increasingly to problems of inductive reasoning and of rational belief and decision. His principal aim was to construct a formal system of inductive logic; its central concept, corresponding to that of deductive implication, would be that of probabilistic implication—or, more precisely, a concept representing the degree of rational credibility or of probability that a given body of evidence may be said to confer upon a proposed hypothesis. Carnap presented a rigorous theory of this kind in his Logical Foundations of Probability (1950).
(Encyclopædia Britannica)

Analytic Philosophy and Pragmatism

Like pragmatism, logical positivism, or logical empiricism, falls within the empiricist tradition, The logical positivists subscribed to the central thesis of the empiricists that only statements about sensory phenomena are genuine, and took this as their guide when discussing meaning, truth, and inquiry. For the logical positivists, meaningful empirical statements come only in two flavors: (1) statements that are cast directly in observational language; and (2) statements that can be reduced to, or translated into, statements that are cast directly in observational language. The translation, or reduction, must abide by the formation and transformation rules of first order predicate logic (what counts as a well-formed sentence, how to derive one sentence from another while preserving truth, etc.)

Carnap’s 1928 Der logische Aufbau der Welt is the most ambitious product of this approach. The aim of the book is to reduce all claims about reality to claims about the given. For Carnap, this means showing how each meaningful statement is in effect a logical construction of so-called observation sentences, which are sentences that capture raw, unanalyzed perceptual data, purportedly without any conceptual pollution.

In light of this, the logical positivists’ answer to the search for meaning is relatively straightforward. The meaning of any statement, words, etc., is the observation statement into which they can be translated, while giving particular attention to the relations between those observation statements.
Modern logic, they think, gives us a perfect and transparent medium by which those relations could be expressed precisely and unambiguously. For the logical positivists, knowledge is a matter of grasping those relations. It is not concerned with the content of our experience – which is private and non-communicated. It is the logical structure that renders concepts inter-subjective. Thus it is not someone’s unique and private experience that constitutes knowledge, but how this experience fits within a larger structure that is communicable.

For the linguistically oriented logical positivists, this comes down to the question of how to relate experience to a language (the medium in which we express and communicate our thought), where “language” is to be interpreted broadly as “a set of symbols which are to be combined in accordance with a definite logical syntax” with the purpose “to mirror or express facts”. For the logical positivists a statement expresses a fact, not by eliciting certain sensations, but through its with the fact. A statement is true if its components correctly reflect the components of the fact it expresses; it is false if they don’t.
This idea of knowledge as a mirror of realty is radically rejected by the pragmatists. It is explicitly criticized by Dewey and later becomes the focal point of Richard Rorty’s criticism of contemporary philosophy in .

Carnap’s Principle of Tolerance

Carnap holds that the role of philosophy is to analyze and clarify the language of science, and to formulate and recommend alternative languages. He holds that there are languages which differ in expressive power, not merely as notational variants. (The difference between intuitionistic logic and classical logic is an important example here, as is the difference between the language of Newtonian mechanics and the language of relativistic mechanics.) He also holds that there is no one correct language. Different languages may be useful for different purposes; it is no part of the philosopher’s job to prescribe this or that language, merely to analyze, to clarify, and to suggest alternatives. This idea has become known as the Principle of Tolerance; from the 1930s on, it is fundamental to Carnap’s view of what philosophy is and how it differs from science. (That there is such a difference is a point which Carnap never questions.)

The Principle of Tolerance requires that, for any language, there be a clear difference between the analytic sentences of the language and its synthetic sentences. The former are (roughly) those which are constitutive of the language: if we change our mind about the truth of such a sentence we have, in effect, adopted a new language. Carnap speaks of a change of this sort as external, since it involves a change of language. A change of mind about an ordinary synthetic sentence is, by contrast, internal, since it takes place within a given language. External changes are a matter for tolerance, whereas internal changes are correct or incorrect, not matters to which we should apply the Principle of Tolerance. For the principle to make sense, each sentence of the language must fall clearly into the one category or the other.

At least as Quine sees the matter, the use of the Principle of Tolerance also requires that analytic sentences be on an entirely different epistemological footing from synthetic sentences. Synthetic sentences are answerable to evidence; analytic sentences are a matter of the choice of language, which does not require theoretical justification.

Verification Principle of Meaning

The logical positivists saw an intimate connection between meaning and verification that went much further than the classic observation that before you can verify a statement you must first know what it means. They maintained the much more radical thesis that questions of meaning and of verification come down to the same. As Carnap puts it in “Testability and Meaning”, to know the meaning of a sentence is to know what it would be for that sentence to be found true. This view entails that “if for two sentences the conditions under which we would have to take them as true are the same, then they have the same meaning” (Testability and Meaning, p420). In brief, for the logical positivists, the meaning of a proposition is its method of verification. This view is known as verificationism, and the logical positivists’ criterion of meaning is called the verification principle. This principle plays a role not unlike that of the pragmatic maxim in pragmatism.

The logical positivists first maintained a strong version of the principle on which a statement is meaningful if and only if it can be conclusively shown true or false by relating it to sensory experiences. To know the meaning of a statement is knowing how to translate it into observation sentences. For example, “This teacup is fragile” would mean “If this teacup is dropped on the floor, it will break”.

This version of the verification principle quickly proved too restrictive. For one thing, it called all statements about the past and about the future meaningless because such statements cannot be conclusively verified. … Later versions of the verification principle relaxed the requirement that for a statement to be meaningful we must be able to conclusively show it to be true or false. It is to this more moderate version of the principle that Carnap subscribed. As Carnap puts it in Testability and Meaning, “If by verification is meant a definitive and final establishment of truth, then no (synthetic) sentence is ever verifiable” (p420). According to Carnap we can only confirm a sentence more and more, thereby increasing our confidence that the sentence is true. For Carnap, a sentence is confirmable if we know what conditions would confirm the sentence. Besides confirmability, Carnap also introduced the stronger notion of testability. A sentence is testable if we can produce experiments at will that would lead to its confirmation or dis confirmation. The notion of confirmability is wider, as not all sentences that are confirmable are also testable. Carnap distinguishes four types of empiricism depending on whether we require that every synthetic sentence is testable, completely testable, confirmable, or completely confirmable. Carnap himself favors the third and most liberal type.

The basic thesis of empiricism, in a familiar but quite vague formulation, is that all concepts and beliefs concerning the world ultimately derive from immediate experience. In some of his most important writings, Carnap sought, in effect, to give this idea a clear and precise interpretation. Setting aside, as a psychological rather than a philosophical problem, the question of how human beings arrive at their ideas about the world, he proceeded to construe empiricism as a systematic-logical thesis about the evidential grounding of empirical knowledge. To this end, he gave the issue a characteristically linguistic turn by asking how the terms and sentences that, in scientific or in everyday language, serve to express assertions about the world are related to those terms and sentences by which the data of immediate experience can be described. The empiricist thesis, as construed and defended by Carnap, then asserts that the terms and sentences of the first kind are “reducible” to those of the second kind in a clearly specifiable sense. Carnap’s conception of the relevant sense of reducibility, which he always stated in precise logical terms, was initially rather narrow but gradually became more liberal.

In his first great work, Der logische Aufbau der Welt (1928; The Logical Structure of the World), Carnap developed, with unprecedented rigour, a version of the empiricist reducibility thesis according to which all terms suited to describe actual or possible empirical facts are fully definable by terms referring exclusively to aspects of immediate experience, so that all empirical statements are fully translatable into statements about immediate experiences.

Prompted by discussions with his associates in Vienna, Carnap soon began to develop a more liberal version of empiricism, which he elaborated while he was professor of natural philosophy at the German University in Prague (1931–35); he eventually presented it in full detail in his essay “Testability and Meaning” (1936–37). Carnap argued that the terms of empirical science are not fully definable in purely experiential terms but can at least be partly defined by means of “reduction sentences,” which are logically much-refined versions of operational definitions, and “observation sentences,” whose truth can be checked by direct observation. Carnap stressed that usually such tests cannot provide strict proof or disproof but only more or less strong “confirmation” for an empirical statement.

Sentences that do not thus yield observational implications and therefore cannot possibly be tested and confirmed by observational findings were said to be empirically meaningless. By reference to this testability criterion of empirical significance, Carnap and other logical empiricists rejected various doctrines of speculative metaphysics and of theology, not as being false but as making no significant assertions at all.

Carnap argued that the observational statements by reference to which empirical statements can be tested may be construed as sentences describing directly and publicly observable aspects of physical objects, such as the needle of a measuring instrument turning to a particular point on the scale or a subject in a psychological test showing a change in pulse rate. All such sentences, he noted, can be formulated in terms that are part of the vocabulary of physics. This was the basic idea of his “physicalism,” according to which all terms and statements of empirical science—from the physical to the social and historical disciplines—can be reduced to terms and statements in the language of physics.

In later writings, Carnap liberalized his conception of reducibility and of empirical significance even further so as to give a more adequate account of the relation between scientific theories and scientific evidence.

The Analytic-Synthetic Distinction

German philosopher Immanuel Kant had made a distinction between analytic and synthetic statements and a priori and a posteriori ones. This made possible a fourfold classification of statements: analytic and synthetic a priori, and analytic and synthetic a posteriori. Everyone agreed that all analytic statements are a priori, so the analytic a posteriori category is empty. But what about synthetic a priori statements—statements that say something new about the world in that the predicate is not merely "contained in" the subject, but are also known before or apart from experience?

Kant claimed that this is not an empty category, and he gave some mathematical and philosophical statements as examples. But the logical empiricists claimed that there are no such statements; that there are only two kinds of statements, the analytic a priori ones and the synthetic a posteriori ones. Much of Carnap's work was based on this conviction and his subsequent attempt to distinguish precisely between analytic and synthetic statements—a conviction and program that was central to all the logical positivists or logical empiricists, but that was rejected in Quine's seminal essay, Two Dogmas of Empiricism (1951).
(New World Encyclopedia)

One idea in logic and the theory of knowledge that occupied much of Carnap’s attention was that of analyticity. In contrast to the 19th-century radical empiricism of John Stuart Mill, Carnap and other logical empiricists held that the statements of logic and mathematics, unlike those of empirical science, are analytic—i.e., true solely by virtue of the meanings of their constituent terms—and that they can therefore be established a priori (without any empirical test). Carnap repeatedly returned to the task of formulating a precise characterization and theory of analyticity. His ideas were met with skepticism by some, however—among them Quine, who argued that the notion of analytic truth is inherently obscure and the attempt to delimit a class of statements that are true a priori should be abandoned as misguided.
(Encyclopædia Britannica)

The Analytic-Synthetic Distinction and the Argument Against Logical Empiricism

The philosophers who most influenced Quine were the Logical Empiricists (also known as Logical Positivists), especially Rudolf Carnap. The distinction between analytic truths and synthetic truths plays a crucial role in their philosophy. Analytic truths might be characterized as those true solely in virtue of the meanings of the words they contain; synthetic truths, by contrast, state matters of extra-linguistic fact, and are known by experience. The Logical Empiricists accounted for truths which do not seem to be answerable to experience, most obviously the truths of logic and mathematics, by saying that they are analytic, and this position was very widely held by the 1940s. Quine, however, famously casts doubt on analytic-synthetic distinction, and rejects the use made of it by the Logical Empiricists and other philosophers from the 1930s on. (Notable among the others is C. I. Lewis, first a teacher and then a colleague of Quine; his influence on Quine has perhaps been underestimated.)
The issues here are complex, and the argument takes many twists and turns. The aim of this section is to give an account of Quine’s mature view, and of the strongest arguments that he has for it. (Stanford Encyclopedia of Philosophy: Willard van Orman Quine)

The central disagreement between Carnap and Quine was over analyticity—a term in technical philosophy—and has to do with the problem in epistemology of how we can justify our beliefs. Carnap tried to use the principle of verificationsim, coupled with an anitmetaphysical stance, to avoid reliance on intuition. Instead Carnap proposed that basic beliefs—the things that had been regarded as relying on intuitions—should be regarded as definitions. Reliance on intuitions implies or at least suggests that there is a realm of truths beyond and independent of ourselves to which we somehow gain access through intuition; the problem has always been that we cannot show that these intuitions are accurate. Carnap's proposal was that these basic claims or beliefs are something we make ourselves, so no question can arise about whether they are "true" or "veridical." "One consequence of Carnap's theory is that the basic metaphysical commitments, logical rules, epistemic principles, and so on are language-dependent, that is, that they depend on what definitions are chosen. If you choose differently from me, we do not thereby disagree; we merely speak different languages" (Creath 1990, 7). Languages, of course, are neither true nor false; the only criterion is that some may be more convenient than others.

According to Carnap's view, basic claims and their logical consequences are true because of their meanings, and the basic claims can be known through an analysis of the meanings of the terms in them. Those claims that are true in virtue of their meanings are analytic according to Carnap.

Quine, a younger man than Carnap—but one who possessed at least as strong logical and analytic skills as Carnap—did not object to Carnap's view because he wanted to defend the philosophical systems that Carnap undermined, and he was in favor of Carnap's tie-in between logic and philosophy. Quine's final objection to Carnap's method was based on Quine's conclusion that the idea or analyticity is unintelligible, so the supposed distinction between analytic and synthetic statements cannot be upheld.

Quine offered three arguments for his view. First, no one has succeeded in clarifying the notion of analyticity. Second, constructed languages such as those Carnap produced do not clarify the notion of analyticity. All Carnap did was define analyticity in L, but that does not clarify or define the term 'analytic.' Third, in science and elsewhere, we are able and willing to modify anything, even our basic notions of analytic logic, if there are good (pragmatic) reasons for doing so. Thus the supposed distinction between what is known analytically and what is known synthetically breaks down.
(New World Encyclopedia)

Excerpt and Condensation from Quine's Two Dogmas of Empiricism

Modern empiricism has been conditioned in large part by two dogmas.
1. The fundamental cleavage between truths which are analytic and truths which are synthetic.
2. Reductionism: the belief that each meaningful statement is equivalent to some logical construct upon terms which refer to immediate experience.
Quine argues that both dogmas are ill-founded and one effect of abondoning them is a blurrind of the supposed boundary between speculative metaphysics and natural science. Another effect is a shift toward pragmatism.

(1) Analyticity
From the use Kant makes of the notion of analyticity, it can be restated like this: a statement is analytic when it is true by virtue of meanings and independently of fact.

Analytic statements fall into two classes:
1. Those of the first class may be called logically true, are typified by:
      No unmarried man is married.
This statement remains true under any and all reinterpretations of ‘man’ and ‘married’.
2. But there is also a second class of analytic statements, typified by:
      No bachelor is married.
The characteristic of such a statement is that it can be turned into a logical truth by putting synonyms for synonyms; thus second statement can be turned into the first by putting ‘unmarried man’ for its synonym ‘bachelor’.
According to Quine, a major difficult of the analyticity lies in the second class, which depends on the notion of synonymy.

(2) Definition
Quine finds that definition – except in the extreme case of the explicitly conventional introduction of new notation – hinges on prior relations of synonymy. He thus maintains that the notion of definition does not hold the key to synonymy and analyticity.

(3) Interchangeability
A natural suggestion is that the synonymy of two linguistic forms consists simply in their interchangeability in all contexts without change of true value.
But it is not quite true that the synonyms ‘bachelor’ and ‘unmarried man’ are everywhere interchangeable.
Upon close examination, Quine finds that interchangeability is not a sufficient condition of cognitive synonymy in the sense needed for deriving analyticity.

Thus, “Analyticity at first seemed most natural definable by appeal to a realm of meanings. On refinement, the appeal to meanings gave way to an appeal to synonymy or definition. But definition turned out to be a will-o’-the wisp, and synonymy turned out to be best understood only by dint of a prior appeal to analyticity itself. So we are back at the problem of analyticity.”

(4) Semantical rules
It is often hinted that the difficulty in separating analytic statements from synthetic ones in ordinary language is due to the vagueness of ordinary language and that the distinction is clear when we have a precise artificial language with explicit “semantical rules”.
In this section, Quine shows that this is a confusion.
Quine shows that semantical rules determining the analytic statements of an artificial language are of interest only in so far as we already understand the notion of analyticity; they are of no help in gaining this understanding.

“It is obvious that truth in general depends on both language and extralinguistic fact. The statement ‘Brutus killed Caesar’ would be false if the world had been different in certain ways, but it would also be false if the word ‘killed’ happened rather to have the sense of ‘beget’. Thus one is tempted to suppose in general that the truth of a statement is somehow analyzable into a linguistic component and a factual component. Given this supposition, it next seems reasonable that in some statements the factual component should be null; and these are the analytic statements. But, for all its a priori reasonableness, a boundary between analytic and synthetic statements simply has not been drawn. That there is such a distinction to be drawn at all is an unempirical dogma of empiricists, a metaphysical article of faith.”

(5) The verification theory and reductionism
The verification theory of meaning is that the meaning of a statement is the method of empirically confirming of infirming it. Analytic statement is that limiting case which is confirmed no matter what.
What the verification theory says is that statements are synonymous if and only if they are alike in point of method of empirical confirmation or infirmation.

This is an account of cognitive synonymy not of linguistic forms generally, but of statements. However, from the concept of synonymy of statements we could derive the concept of synonymy for other linguistic forms.
So, if the verification theory can be accepted as an adequate account of statement synonymy, the notion of analyticity is saved after all. However, if statement synonymy is said to be likeness of method of empirical confirmation or infirmation, just what are these methods which are to be compared for likeness? What, in other words, is the nature of the relation between a statement and the experiences which contribute to or detract from its confirmation?

Reductionism, in its radical form, is the view that every meaningful statement is held to be translatable into a statement (true or false) about immediate experience.
Carnap embarked on this project in his Aufbau. However, in his later writings he abandoned all notion of the translatability of statements about the physical world into statements about immediate experience. Reductionism in its radical form has long since ceased to figure in Carnap’s philosophy.

But the dogma of reductionism has, in a subtler and more tenuous form, continued to influence the thought of empiricists. The notion lingers that to each synthetic statement, there is associated a unique range of possible sensory events such that the occurrence of any of them would add to the likelihood of truth of the statement, and that there is associated also another unique range of possible sensory events whose occurrence would detract from the likelihood. This notion is of course implicit in the verification theory of meaning.

The dogma of reductionism survives in the supposition that each statement, taken in isolation from its fellows, can admit of confirmation or infirmation at all.

The dogma of reductionism, even in its attenuated form, is intimately connected with the other dogma – that there is a cleavage between the analytic and the synthetic.
The two dogmas are, indeed, at root identical. Upon reflection that in general the truth of statements does obviously depend both upon language and upon extralinguistic fact; and that this obvious circumstance carries in its train, not logically but all too naturally, a feeling that the truth of a statement is somehow analyzable into a linguistic component and a factual component. The factual component must, for empiricists, boil down to a range of confirmatory experience. In the extreme case where the linguistic component is all that matters, a true statement is analytic. However, Quine maintains that the distinction between analytic and synthetic can’t easily be drawn. His suggestion is that it is nonsense to speak of a linguistic component and a factual component in the truth of any individual statement. Taken collectively, science has its double dependence upon language and experience; but this duality is not significantly traceable into the statements of science taken one by one.

The idea of defining a symbol in use was an advance over the impossible term-by-term empiricism of Locke and Hume. The statements, rather than the term, came with Frege to be recognized as the unit accountable to an empiricist critique. But what Quine urges is that even in taking the statement us unit we have drawn our grid too finely. The unit of empirical significance is the whole of science.

(6) Empiricism without the dogmas
The totality of our so-called knowledge or beliefs is a man-made fabric which impinges on experience only along the edge.
If this view is right, it is misleading to speak of the empirical content of an individual statement – especially if it is a statement at all remote from the experiential periphery of the field. Furthermore it becomes folly to seek a boundary between synthetic statements, which hold contingently on experience, and analytic statements, which hold come what may. Any statement can be held true come what may, if we make drastic enough adjustments elsewhere in the system. Conversely, by the same token, no statement is immune to revision.

As a empiricist Quine continues to think of the conceptual scheme of science as a tool, ultimately, for predicting future experience in the light of past experience. Physical objects are conceptually imported into the situation as convenient intermediates – not by definition in terms of experience, but simply as irreducible posits.
Positing does not stop with macroscopic physical objects. Objects at the atomic level are posited to make the laws of macroscopic objects, and ultimately the laws of experience, simpler and more manageable; and we need not expect or demand full definition of atomic and subatomic entities in terms of macroscopic ones, any more than definition of macroscopic things in terms of sense data. Science is a continuation of common sense, and it continues the common-sense expedient of swelling ontology to simplify theory.
Ontological questions, under this view, are on a par with questions of natural science.

Carnap, Lewis, and others take a pragmatic stand on the question of choosing between language forms, scientific frameworks; but their pragmatism leaves off at the imagined boundary between the analytic and the synthetic. In repudiating such a boundary Quine espouses a more thorough pragmatism. Each man is given a scientific heritage plus a continuing barrage of sensory stimulation; and the considerations which guide him in warping his scientific heritage to fit his continuing sensory promptings are, where rational, pragmatic.

Two Dogmas of Empiricism, an Explanaton

Quine’s arguments regarding analyticity go something like this.

Given that the concept of a logical truth – “No unmarried man is married” – is well-defined, we might define analytic statements as those statements that can be turned into logical truths, by substituting synonymous expressions.
Thus, we can turn “No bachelor is unmarried” into “No unmarried man is unmarried,” by substituting the terms ‘bachelor’ and ‘unmarried man’, which are synonymous.

This, of course, requires that we have some account of synonymy. It is tempting to simply say that two terms are synonymous if they have the same meaning, but this presupposes that we have an appropriate notion of meaning to work with. Indeed, analyticity belongs to a tight-knit family of concepts – analyticity, synonymy, meaning – all of which need explaining, so it does us no good simply to explain one in terms of the other.

The way to define synonymy, Quine says, is by way of substitutability. Two expressions are synonymous if they are substitutable, in and out of sentences, without changing the truth value of those sentences. But this may not be sufficient. After all, in ordinary semantic contexts, substitutability is merely a test for co-referentiality, not synonymy. For example, the word ‘nine’ in the sentence ‘nine is less than ten’ can be substituted with the expression ‘the number of planets in the solar system’, without changing the truth value of the sentence. And while they certainly are co-referential – the two expressions both refer to the number 9 – they are not synonymous.

If, however, we consider semantic contexts beyond the ordinary, such as modal contexts – say a sentence of the form “Necessarily, X is F,” then substitutability does seem to be a test for synonymy. We can see, for example, that we cannot substitute ‘nine’ in the sentence “Necessarily, nine is less than ten,” with ‘the number of planets’, without a change in truth value. After all, while it is true that the number of solar system in our planets is less than ten, it is not a necessary truth. This shows, then, that ‘nine’ and ‘the number of planets in the solar system’, while co-referential, are not synonymous and that only synonymous expressions will be substitutable in and out of a “Necessarily” sentence.

So, perhaps we could define synonymy as “substitutability everywhere, including sentences stating necessary truths and falsehoods.” Having thus defined synonymy, we can then define analyticity, in terms of logical truth.

It is at this point that Quine pulls his last and most clever trick. The account we have just given is circular or at least, effectively circular. For the only necessary truths are the analytic ones, which means that to define synonymy in terms of substitutability and necessary truth is to presuppose that we already have an account of analyticity, which is what we were looking for, in the first place.

In response to the second Empiricist idea – that individual statements have their own verification conditions – Quine introduces what will become the very well-known and much-discussed “Web of Belief”; the idea that the various statements we assent to are, in the immediate sense, dependent upon one another for confirmation, much like the strands of a spider’s web are all connected and mutually-supporting, and only are confirmed by experience as a group, at the web’s boundaries, where it connects to the world. Thus, ultimately, all substantive statements – even the statements of mathematics – are confirmed empirically, although it may take disconfirmation across a wide span of the web to reveal the falsity of such statements, which lie near its center.

This paper, along with his book, Word and Object (1960), set much of the agenda for analytic philosophy, after the Second World War and is one of the most widely cited philosophy papers of the 20th century.

Quine’s Alternative

If logic, mathematics, and other putatively a priori parts of our knowledge, are not to be explained by analyticity, how are they to be accounted for? Holism, which is central to Quine’s argument against Carnap, also provides him with an alternative position. Logic and mathematics seem to have a special status because they are independent of experience. They appear to be necessary and not susceptible of refutation by what future experience brings; they appear to be a priori because we know them independent of experience. Carnap sought to explain these appearances by appealing to the idea that accepting an analytic sentence goes with speaking the language, and to the Principle of Tolerance. Since choice of language is not justified by experience, the truth of the analytic sentences of a given language is not answerable to experience.

How is Quine to explain the apparent necessity and a priori status of some truths without appeal to the Principle of Tolerance? To take the second point first: Quine’s holism is the view that almost none of our knowledge is directly answerable to experience. (The exceptions are what he calls ‘observation sentences’) In almost all cases the relation is indirect: a given sentence is only answerable to experience if a significant body of theory is presupposed. (When we say that a given observation confirms or refutes a given theoretical claim, we are tacitly presupposing much theoretical knowledge.) This is most easily seen if we consider a highly theoretical sentence, of theoretical physics, perhaps, but in Quine’s view it holds, of almost all our sentences. The reason to accept a sentence is its contribution to the success of theory as a whole as an efficient and simple method of dealing with and predicting experience; in principle, this means the success of our theory as a whole, the whole body of sentences that we accept, in dealing with experience as a whole.

This statement, in Quine’s view, holds with full generality. In particular, it applies to the sentences of logic and mathematics as much as any other subject. No particular experience confirms ‘2 + 2 = 4’; Quine is not advancing what Frege derided as a ‘gingerbread and pebble’ account of arithmetic, in which the sentence is justified by our observations of cookies or stones. But Quine does hold that the sentence, and the theory of arithmetic of which it is an inseparable part, earns its place in our body of knowledge by contributing to the overall success of that body of knowledge in dealing with experience as a whole.

As for the apparent necessity of some sentences, Quine appeals to holism to explain that too. Some sentences have great systematic import for our knowledge as a whole. (In Quine’s well-known metaphor, they stand near the centre of the ‘web of belief’.) The truths of elementary arithmetic are an example: they play a role in almost every branch of systematic knowledge. For this reason, we cannot imagine abandoning elementary arithmetic. Doing so would mean abandoning our whole system of knowledge, and replacing it with an alternative which we have not even begun to envisage. Nothing in principle rules out the possibility that the course of experience will be such that our present system of knowledge becomes wholly useless, and that in constructing a new one we find that arithmetic is of no use. But this is a purely abstract possibility, certainly not something we can imagine in any detail. So the idea that we might reject arithmetic is likewise unimaginable.

Meaning and Quinean Analyticity

The idea of meaning, and sameness of meaning, occupies a crucial role in the debate over analyticity.
Quine maintains that “no statement is immune to revision”. Carnap agrees. However, he would insist that in the case of analytic sentences, a revision involves a change of language, and thus of the meaning of the words used in the sentence.
In Quine’s arguments against the analytic-synthetic distinction, he seeks to cast doubt on the idea that there is a notion of meaning which is clear enough to use in defining a notion of analyticity.
According to Carnap’s version of ‘Verification Principle of Meaning’, the meaning of a sentence is given by the experiences which would confirm it; holism, however, implies that the idea of confirmation does not apply to individual sentences, considered in isolation from the theories of which they are parts.
*Note: Quine’s scepticism about the idea of meaning is much criticized. But Quine’s scepticism about meanings does not lead to any scepticism about meaningfulness. - (Stanford Encyclopedia of Philosophy)

Quine's Holism

Holism is the claim that most of our sentences do not have implications for experience when they are taken one-by-one, each in isolation from the others. What has experiential implication is, in most cases, not an individual sentence but a larger chunk of theory. Holism is not a very controversial doctrine. Carnap accepts it, but Quine holds that he does not think through its implications far enough. In particular, Quine claims that holism shows that most of our sentences are not justified by the relation of the individual sentence, considered in isolation, to experience. Almost always, what matters is the relation to experience of some larger chunk of theory (and, in principle, although perhaps never in practice, of the theory as a whole). This means that the correctness of a given claim is almost never settled simply by gathering empirical evidence. Other factors will play a role, in particular the way in which accepting that claim would contribute to the efficacy and simplicity of the theory as a whole. But these are precisely the ‘pragmatic factors’ which Carnap thought played a role in the choice of language. In arguing that such factors play a role throughout our knowledge, Quine accepts ‘a more thorough pragmatism’ which puts Carnap’s external changes on the same epistemological status as his internal changes.

Quine-Dubem Thesis (Dubem-Quine Thesis)

The point that scientific theories are not proved, nor even, strictly speaking, disproved, by the kinds of observation that confirm or disconfirm them is developed by Pierre Duhem in The Aim and Structure of Physical Theory (translated by Philip P. Wiener 1964); and the idea which explains this – that theories are tested in conjunction with a number of related hypotheses and assumptions rather than in isolate - is developed by W.V. Quine. (See Pursuit of Truth by Quine and Philosophy of Natural Science by Carl G. Hempel, 1966).

Naturalized epistemology

Quine is important in philosophy of science for his "systematic attempt to understand science from within the resources of science itself" and for his conception of philosophy as continuous with science.
The aim of "Naturalized epistemology" was to answer all substantive questions of knowledge and meaning using the methods and tools of the natural sciences.

"Epistemology, or something like it, simply falls into place as a chapter of psychology and hence of natural science. It studies a natural phenomenon, viz., a physical human subject. This human subject is accorded a certain experimentally controlled input — certain patterns of irradiation in assorted frequencies, for instance — and in the fullness of time the subject delivers as output a description of the three-dimensional external world and its history. The relation between the meager input and the torrential output is a relation that we are prompted to study for somewhat the same reasons that always prompted epistemology: namely, in order to see how evidence relates to theory, and in what ways one's theory of nature transcends any available evidence...But a conspicuous difference between old epistemology and the epistemological enterprise in this new psychological setting is that we can now make free use of empirical psychology." (Quine's Epistemology Naturalized, 1969: 82–3)

Richard Rorty, in his obituary for Quine, put it this way:
"Quine shared the usual Anglophone distaste for Heidegger, and he obviously did not want to bring back the sort of speculative metaphysics that had been produced by, for example, F.H. Bradley and A.N. Whitehead. But he did not offer a metaphilosophical program to replace the one that Russell and Carnap had put forward. Rather, he simply urged philosophers to bring philosophy into contact with empirical science—to stop trying for necessary truths and to instead find perspicuous ways of arranging the materials that natural science provides. He envisaged, for example, a future in which epistemology, the philosophical study of knowledge, would be 'naturalized' and, thus, absorbed in what we now call 'cognitive science.' That sort of collaboration with empirical inquiry now seems to many Anglophone philosophers the best way to advance their discipline." (Chronicle of Higher Education obituary for W V Quine - Feb. 2, 2001)

Introduction to the Thirtieth-Anniversary Edition of "Philosophy and the Mirror of Nature" by Michael Williams

EXCERPTS
It is the single greatest influence on the revival of American Pragmatism, one of the most exciting developments in philosophy today.

Rorty sees philosophy, as it came to be understood in the last century, as an attempt to work through the consequences of a conception of knowledge as accurate representation, a conception rooted in the metaphor of mind as the mirror of nature. From its seventeenth-century origins, principally in the writings of Descartes, this metaphor leads to the emergence of what Rorty calls “philosophy-as-epistemology,” with its canonical list of textbook problems: the mind-body problem, skepticism, the nature of truth, and the rest. According to Rorty, we should not keep trying to solve such problems, which have evolved into forms designed to resist solution. Better to put them behind us.

Rorty takes a different approach. His way out of philoso­phy-as-epistemology turns on a broadly pragmatic outlook that he calls “epistemological behaviorism.” Epistemological behaviorism is not a commitment to reduce mental activity to overt behavior but a methodological stance. As an episte­mological behaviorist, he examines human thought and knowledge from a public, third-person standpoint, treating language as communicative and knowledge as the result of argument and discussion. Differences lacking practical im­port have no theoretical significance either.

Rorty’s epistemological-behaviorist stance is a paradigm of pragmatism.
According to Macarthur and Price, who acknowledge Rorty’s influence, contemporary pragmatism combines two commitments. The first is to linguistic priority: don’t start by asking about the nature of mind, knowledge, etc.; start by asking what we are doing in deploying mentalistic or epistemological vocabu­lary. This is very much how Rorty proceeds. The second is to antirepresentationalism, which counsels us to avoid approaching our various vocabularies in ways that make theoretical use of representationalist notions such as truth (as corre­spondence to fact) or reference (e.g., as some naturalistically explicable word-world relation). Antirepresentationalism -- the rejection of the idea of mind (or language) as the mirror of nature -- is the leitmotif of Rorty’s book.

On Rorty’s antirepresentationalist view, language is better understood as a set of tools rather than as the mirror of na­ture. Like new tools, new ways of talking do not simply enable us to cope better with existing projects and problems: they give us new things to do. In the light of new problems and projects, old ways of talking may come to seem more trouble than they are worth, in which case problems couched in their terms may reasonably be dropped.

BOOK REVIEWS: "Philosophy and the Mirror of Nature"

EXCERPTS
Rorty strikes a deathblow to modern European philosophy by telling a story about the emergence, development and decline of its primary props: the correspondence theory of truth, the notion of privileged representations and the idea of a self-reflective transcendental subject. Rorty's fascinating tale—his-story —is regulated by three fundamental shifts which he delineates in detail and promotes in principle: the move toward anti-realism or conventionalism in ontology, the move toward the demythologizing of the Myth of the Given or anti-foundationalism in epistemology, and the move toward detranscendentalizing the subject or dismissing the mind as a sphere of inquiry.

The chief importance of Rorty's book is that it brings together in an original and intelligible narrative the major insights of the patriarchs of postmodern American philosophy—W. V. Quine, Wilfred Sellars, and Nelson Goodman— and persuasively presents the radical consequences of their views for contemporary philosophy. Rorty credits Wittgenstein, Heidegger and Dewey for having "brought us into a period of 'revolutionary' philosophy" by undermining the prevailing Cartesian and Kantian paradigms and advancing new conceptions of philosophy. And these monumental figures surely inspire Rorty. Yet, Rorty's philosophical debts—the actual sources of his particular anti-Cartesian and anti-Kantian arguments—are Quine's holism, Sellars' anti-foundationalism, and Goodman's pluralism. In short, despite his adamant attack on analytical philosophy—the last stage of modern European philosophy—Rorty feels most comfortable with the analytical form of philosophical argumentation (shunned by Wittgenstein and Heidegger).