Preface; Chapter I. Introduction; 1. Statement of the Problem 2. Systems Considered 3. Metamathematical Methods of Proof; Chapter II. Over-Simple Interpretations; 1. Trivial Interpretation 2. Failure of Interpretation by Recursive Satisfaction 3. Dependence of the Proof of the Verifiable Formula corresponding to a Theorem; Chapter III. Herbrand Interpretation; 1. The Concept of Herbrand Interpretation 2. Herbrand Interpretation of Elementary Number Theory without Induction 3. Properties of the Interpretation 4. Impossibility of an Herbrand Interpretation of Number Theory with Induction; Chapter IV. The No-Counter-Example Interpretation of Number Theory; 1. Non-constructive Considerations 2. No-Counter-Example Interpretation of Number Theory without Induction 3. No-Counter-Example Interpretation, 1*-Consistency, and External Consistency 4. Ordinal Recursive Functionals, 1*-Consistency of Number Theory with Induction 5. Representation of Ordinal Recursive Functionals in Elementary Number Theory; Chapter V. Ramified Analysis; 1. Description of Systems 2. Ramified Analysis without Induction 3. Recursive Well-orderings and Ordinal Recursive Functionals 4. Ramified Analysis with Induction 5. Representation of Ordinal Recursive Functionals in Ramified Analysis; Chapter VI. ?-Consistency; 1. Critique of the Concept of ?-Consistency 2. ?-Consistency, External Consistency, and 1*-Consistency 3. ?-Consistency of Ramified Analysis; Appendix I. Arithmetization of Schuette's Cut-elimination theorems; Appendix II. Ordinal Functions; Bibliography; Index of Definitions