Part I Meaning and Verification 1 The criterion of significance 2 The a priori and the analytic 3 The principle of verification 4 Is there a rationale for the verification principle? 5 Empirical atomism 6 Ayer’s reductionism 7 The relativity-factor 8 Ayer’s critique of ethics Part II Knowledge and Scepticism 1 Introduction 2 Ayer’s definition of knowledge 3 The truth-reliability thesis 4 Specifying the mode of arrival 5 The reason-furnishing thesis 6 The furnishing of reasons 7 The nature of scepticism 8 The four possible solutions 9 Perception 10 The nature of perceptual experience 11 Sense-experience and the physical world 12 Scepticism reconsidered Part III Man and Nature 1 The problem of induction 2 Hume’s argument 3 A priori probability 4 Ayer’s own position 5 The nomological-explanatory solution 6 Ayer’s account of causation 7 The reducibility thesis 8 The unity of the mind 9 Free will