1. Preface; 2. Motivating examples; 3. Free will and determinism; 4. The principle of indifference; 5. Relative frequencies; 6. Subjective probabilities; 7. A case study; 8. The role of theories; 9. Von Neumann and Morgenstern's theorem; 10. De Finetti's theorem; 11. Savage's theorem; 12. The definition of states; 13. A critique of Savage; 14. Objectivity and rationality; 15. Anscombe-Aumann's theorem; 16. Choquet expected utility; 17. Prospect theory; 18. Maxmin expected utility; 19. Case-based qualitative beliefs; 20. Frequentism revisited; 21. Future research.