Charles Hartshorne is Ashbel Smith Professor of Philosophy at the University of Texas. Paul Weiss is Heffer Professor of Philosophy at The Catholic University of America, Washington, D.C.

• Introduction Preface BOOK I: GENERAL HISTORICAL ORIENTATION Chap. 1: Lessons from the History of Philosophy 1. Nominalism 2. Conceptualism 3. The Spirit of Scholasticism 4. Kant and his Refutation of Idealism 5. Hegelism Chap. 2: Lessons from the History of Science 1. The Scientific Attitude 2. The Scientific Imagination 3. Science and Morality 4. Mathematics 5. Science as a Guide to Conduct 6. Morality and Sham Reasoning 7. The Method of Authority 8. Science and Continuity 9. The Analytic Method 10. Kinds of Reasoning 11. The Study of the Useless 12. Il Lume Naturale 13. Generalization and Abstraction 14. The Evaluation of Exactitude 15. Science and Extraordinary Phenomena 16. Reasoning from Samples 17. The Method of Residual Phenomena 18. Observation 19. Evolution 20. Some A Priori Dicta 21. The Paucity of Scientific Knowledge 22. The Uncertainty of Scientific Results 23. Economy of Research Chap. 3: Notes on Scientific Philosophy 1. Laboratory and Seminary Philosophies 2. Axioms 3. The Observational Part of Philosophy 4. The First Rule of Reason 5. Fallibilism, Continuity, and Evolution BOOK II. THE CLASSIFICATION OF THE SCIENCE Proem: The Architectonic Character of Philosophy Chap. 1: An Outline Classification of the Sciences Chap. 2: A Detailed Classification of the Sciences 1. Natural Classes 2. Natural Classifications 3. The Essence of Science 4. The Divisions of Science 5. The Divisions of Philosophy 6. The Divisions of Mathematics BOOK III: PHENOMENOLOGY CHAP. 1: INTRODUCTION 1. The Phaneron 2. Valencies 3. Monads, Dyads, and Triads 4. Indecomposable Elements Chap. 2: The Categories in Detail A. Firstness 1. The Source of the Categories 2. The Manifestation of Firstness 3. The Monad 4. Qualities of Feeling 5. Feeling as Independent of Mind and Change 6. A Definition of Feeling 7. The Similarity of Feelings of Different Sensory Modes 8. Presentments as Signs 9. The Communicability of Feelings 10. The Transition to Secondness B. Secondness 1. Feeling and Struggle 2. Action and Perception 3. The Varieties of Secondness 4. The Dyad 5. Polar Distinctions and Volition 6. Ego and Non-Ego 7. Shock and the Sense of Change C. Thirdness 1. Examples of Thirdness 2. Representation and Generality 3. The Reality of Thirdness 4. Protoplasm and the Categories 5. The Interdependence of the Categories Chap. 3: A Guess at the Riddle Plan of the Work 1. Trichotomy 2. The Triad in Reasoning 3. The Triad in Metaphysics 4. The Triad in Psychology 5. The Triad in Physiology 6. The Triad in Biological Development 7. The Triad in Physics Chap. 4: The Loom of Mathematics; An Attempt to Develop my Categories from Within 1. The Three Categories 2. Quality 3. Fact 4. Dyads 5. Triads Chap. 5: Degenerate Cases 1. Kinds of Secondness 2. The Firstness of Firstness, Secondness and Thirdness Chap. 6: On a New List of Categories 1. Original Statement 2. Notes on the Preceding Chap. 7: Triadomany BOOK IV: THE NORMATIVE SCIENCES Chap. 1: Introduction Chap. 2: Ultimate Goods Chap. 3: An Attempted Classification of Ends Chap. 4: Ideals of Conduct Chap. 5: Vitally Important Topics 1. Theory and Practice 2. Practical Concerns and the Wisdom of Sentiment 3. Vitally Important Truths Indexes