Ayer - Language, Truth and Logic

p. 13: What is the purpose and method of philosophy? Rejection of the metaphysical thesis that philosophy affords us knowledge of a transcendent reality. 14: Kant also rejected metaphysics in this sense, but whereas he accused metaphysicians of ignoring the limits of the human understanding we accuse them of disobeying the rules which govern the significant use of language. 16: Adoption of verifiability as a criterion for testing the significance of putative statements of fact. 16: Distinction between conclusive and partial verification. No propositions can be conclusively verified. 19: Or conclusively confuted. 20: For a statement of fact to be genuine some possible observations must be relevant to the determination of its truth or falsehood. 21: Examples of the kinds of assertions, familiar to philosophers, which are ruled out by our criterion. 24: Metaphysical sentences defined as sentences which express neither tautologies nor empirical hypotheses. 24: Linguistic confusions the prime sources of metaphysics. 27: Metaphysics and Poetry.

p. 30: Philosophy is not a search for first principles. 30: Barrenness of Descartes procedure. 33: The function of philosophy is wholly critical. But this does not mean that it can give an a priori justification of our scientific or common-sense assumptions. 34: There is no genuine problem of induction, as ordinarily conceived. 36: Philosophising is an activity of analysis. 37: Most of those who are commonly thought to have been great philosophers were philosophers in our sense, rather than metaphysicians. 38: Locke, Berkeley, Hume as analysts. 39: We adopt Berkeleys phenomenalism without his theism. 40: And take a Humean view of causation. 43: Philosophy in our sense is wholly independent of metaphysics. We are not committed to any doctrine of atomism. 44: The philosopher as an analyst is not concerned with the physical properties of things, but only with the way in which we speak about them. 45: Linguistic propositions disguised in factual terminology. 46: Philosophy issues in definitions.

p. 48: Philosophy provides not explicit definitions, such as are given in dictionaries, but definitions in use. Explanation of this distinction. 49: Russells theory of descriptions as an example of philosophical analysis. 52: Definition of an ambiguous symbol. 53: Definition of a logical construction. 54: Material things are logical constructions out of sense-contents. 54: By defining the notion of a material thing in terms of sense-contents we solve the so-called problem of perception. 55: A solution of this problem outlined as a further example of philosophical analysis. 59: Utility of such analyses. 59: Danger of saying that philosophy is concerned with meaning. 61: The propositions of philosophy are not empirical propositions concerning the way in which people actually use words. They are concerned with the logical consequences of linguistic conventions. 63: Rejection of the view that every language has a structure concerning which in the language nothing can be said.

p. 64: As empiricists, we must deny that any general proposition concerning a matter of fact can be known certainly to be valid. 64: How then are we to deal with the propositions of formal logic and mathematics?. 67: Rejection of Mills view that these propositions are inductive generalisations. 71: They are necessarily true because they are analytic. 71: Kants definitions of analytic and synthetic judgements. 73: Emendation of Kants definitions. 74: Analytic propositions are tautological; they say nothing concerning any matter of fact. 74: But they give us new knowledge, inasmuch as they bring to light the implications of our linguistic usages. 76: Logic does not describe the laws of thought. 77: Nor geometry the properties of physical space. 80: Our account of a priori truths undermines Kants transcendental system. 81: How, if they are tautological, can there be in mathematics and logic the possibility of invention and discovery?