Overview Is there a priori knowledge? Is there synthetic a priori knowledge? No: Mill, Quine Yes: faculty of a priori intuition (Rationalism, Kant) No: all a priori knowledge analytic (Ayer)
No A Priori Knowledge? J.S. Mill W.V.O. Quine, Two Dogmas of Empiricism
J.S. Mill Maths, logic: a posteriori inductive generalizations E.g. 2+2= 4 true in the past, so likely to be true in the future Because a posteriori, not necessary or universal Merely seem necessary because so well confirmed But: a priori knowledge begins with experience, but does not necessarily arise out of it (Kant, p. 142) Moreover, what could falsify the generalization? Would we accept a counterexample to 2 x 5 = 10? Or just think we had miscounted? (Ayer, p.101). Contrast: all ravens are black
Quine: Two Dogmas of Empiricism 1. The Analytic/Synthetic Distinction Analytic: true in virtue of the meaning of the words involved Synthethic: true in virtue of way the world is E.g. Ayer: a proposition is analytic when its validity depends solely on the definitions of the symbols it contains, and synthetic when its validity is determined by the facts of experience (p. 105) 2. Reductionism, or Verificationism Every meaningful statement can be translated into a statement about experience, or sense-data E.g. Ayer: a sentence is factually significant to any given person if, and only if, he knows how to verify the proposition which it purports to express (p. 48)
1. Analytic/Synthetic Analytic Truths Either logical truths E.g. all unmarried men are unmarried or translatable into a logical truth by substitution of synonyms for synoyms E.g. all bachelors are unmarried But what is meant by synonymous?
Synonymy and Analyticity Synoymous Same Definition? But except for explicit definitions, sameness of definition presupposes synonymy Synoymous Substitutable salve veritate Not mere extensional equivalence: animal with heart and animal with kidneys not synonymous Require ( intensional ) language with necessity : Necessarily, all bachelors are unmarried men But what does necessary mean? For Quine, necessity at least as obscure as analyticity Necessary: yields truth when and only when applied to an analytic statement (pp. 29-30)? Circular!
Analytic/Synthetic? All statements depend on both language and the world The statement Brutus killed Caesar would be false if the world had been different in certain ways, but it would also have been false if the word killed happened rather to have the sense of begat (Quine, p. 36) No statements have null factual component All bachelors are unmarried is true if and only if all bachelors are unmarried The truth predicate points through the sentence to reality : it is about the world!
2. Reductionism Every meaningful statement can be translated into a statement about sense-data (cf. verificationism) Relatedly, there is a unique range of experiences that would confirm or disconfirm any given statement But can meaningful statements be confirmed individually?
The Web of Belief our statements about the external physical world face the tribunal of sense experience not individually but only as a corporate body (p. 41) 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 (p. 43)
The Web of Belief Epistemological holism Theories, background assumptions and auxiliary hypotheses are tested together E.g. discovery of Neptune Even truths of logic can be revised in face of recalitrant experience E.g. Quantum Logic : in QM, it is possible to measure position of particle, or momentum of particle, but not both. In classical logic, every meaningful statement is either T or F In quantum logic, statement indicating position and momentum is neither T nor F but indeterminate
Quine No analytic/synthetic distinction No a priori knowledge No logical necessity
No Analytic/Synthetic Distinction? No analytic/synthetic distinction or an inter-connected network of concepts: analyticity, synonymy, definition, substitutability salva veritate, necessity? Compare: can we understand belief (or for Williamson, knowledge) independent of action, or vice versa?
Indeterminacy of Translation? Quine later argued that there are no facts about synonymy (Word and Object, 1960) For any language, possible to produce two incompatible translation manuals that accommodate all the linguistic evidence E.g. gavagi : rabbit or undetached rabbit part (Cf. epistemological holism: different ways of fitting beliefs to evidence) Facts about meaning indeterminate but is this plausible?
Analytic Truths and Reality Analytic truths: about reality in the same way as synthetic truths? Contrast: all bachelors are unmarried men and bachelors have the highest disposal income. Perhaps: about conventionally determined reality vs. empirical reality? They do not make any assertion about the empirical world. They simply record our determination to use words in a certain fashion (Ayer, p. 112). Note: implies conventionalism about maths. If realism is appealing, then we need a priori intuition
A Priori Intuition Again? How are beliefs about things that are not directly observed justified, e.g. scientific unobservables? Connection between experiences and beliefs cannot be arbitrary, or any set of experiences would support any set of beliefs if experience is φ, then ϕ is (likely to be) true. But how do we know this, if not a priori? So maybe we need a priori intuition after all?
Recap Is there a priori knowledge? Is there synthetic a priori knowledge? No: Mill, Quine Yes: faculty of a priori intuition (rationalism, Kant) No: all a priori knowledge analytic (Ayer)
Further Reading W.V.O. Quine, Two Dogmas of Empiricism, in From a Logical Point of View. (Don t read 4, except for last paragraph.) L. Bonjour and M. Devitt, Is There A Priori Knowledge? in M. Steup and E. Sosa eds. Debates in Contemporary Epistemology (Blackwell, 2005). Devitt s paper is online: http://web.gc.cuny.edu/philosophy/people/d evitt/noaprior.pdf