The concept of probability plays a crucial role in every branch of science and everyday life. Indeed, probability is so important to all of humanity's endeavors that Bishop Butler once said that "probability is the very guide to life" and Henri Poincaré once wrote that "if [the probability] calculus be condemned, then the whole of the sciences must also be condemned." However, despite the ubiquity and importance of the concept of probability, it is surprisingly difficult to say what statements of probability mean. What do we mean when we say something has a certain probability? To answer this question is to give an interpretation of probability. In this talk, Professor Lyon will give a critical overview of the leading interpretations of probability: the classical, logical, frequentist, propensity, subjective, and best-system interpretations of probability.