Introduction. The Idea of a Science of Belief Systems 1. You Don't Know What It's Like! 2. A Descriptive Science of Logic 3. Some Notes on Affect 4. Elements of Comparative Method 5. Belief Systems and the Materialist Conception of History 6. Beliefs That Are Not Supposed To Be Wholly Believed 7. A Theory of Superstition, in Thirteen Paragraphs 8. Believing in Fictional Beings Instead of a Conclusion Appendix. The Use of Symbolic Notation in Descriptive Logic Bibliography