INTRODUCTION On the Sources of Knowledge and of Ignorance CONJECTURES 1 Science: Conjectures and Refutations Appendix: Some Problems in the Philosophy of Science 2 The Nature of Philosophical Problems and their Roots in Science 3 Three Views Concerning Human Knowledge 4 Towards a Rational Theory of Tradition 5 Back to the Presocratics 6 A Note on Berkeley as Precursor of Mach and Einstein 7 Kant’s Critique and Cosmology 8 On the Status of Science and of Metaphysics 9 Why are the Calculi of Logic and Arithmetic Applicable to Reality? 10 Truth, Rationality, and the Growth of Scientific Knowledge REFUTATIONS 11 The Demarcation Between Science and Metaphysics 12 Language and the Body-Mind Problem 13A Note on the Body-Mind Problem 14 Self-Reference and Meaning in Ordinary Language 15 What is Dialectic? 16 Prediction and Prophecy in the Social Sciences 17 Public Opinion and Liberal Principles 18 Utopia and Violence 19 The History of Our Time: An Optimist’s View 20 Humanism and Reason