Pt. I. Introduction to the Logic of Science. 1. A Survey of Some Fundamental Problems. 2. On the Problem of a Theory of Scientific Method -- Pt. II. Some Structural Components of a Theory of Experience. 3. Theories. 4. Falsifiability. 5. The Problem of the Empirical Basis. 6. Degrees of Testability. 7. Simplicity. 8. Probability. 9. Some Observations on Quantum Theory. 10. Corroboration, or How a Theory Stands up to Tests. App. i. Definition of the Dimension of a Theory -- App. ii. The General Calculus of Frequency in Finite Classes -- App. iii. Derivation of the First Form of the Binomial Formula -- App. iv. A Method of Constructing Models of Random Sequences -- App. v. Examination of an Objection. The Two-Slit Experiment -- App. vi. Concerning a Non-Predictive Procedure of Measuring -- App. vii. Remarks Concerning an Imaginary Experiment -- New Appendices. i. Two Notes on Induction and Demarcation, 1933-1934. ii. A Note on Probability, 1938. iii. On the Heuristic Use of the Classical Definition of Probability. iv. The Formal Theory of Probability. v. Derivations in the Formal Theory of Probability. vi. On Objective Disorder or Randomness. vii. Zero Probability and the Fine-Structure of Probability and of Content. viii. Content, Simplicity, and Dimension. ix. Corroboration, the Weight of Evidence, and Statistical Tests. x. Universals, Dispositions, and Natural or Physical Necessity. xi. On the Use and Misuse of Imaginary Experiments, Especially in Quantum Theory. xii. The Experiment of Einstein, Podolsky and Rosen. A Letter from Albert Einstein, 1935.