This book investigates the fundamental nature of probability by examining its role in both objective physical systems and subjective human belief. D. H. Mellor, a prominent philosopher of science, provides a rigorous examination of the competing interpretations of probability, including frequentist, propensity, and Bayesian accounts. He constructs a framework that reconciles the mathematical utility of probability with its philosophical implications for causality and decision theory.

Experts recognize this work as a foundational text for students of philosophy and the philosophy of science. Readers frequently note the academic density of the prose, which requires a solid grasp of logical notation and formal reasoning to fully appreciate the author's arguments.