Probability played its first central role in physical explanations in the theory of heat. Kinetic theory and statistical mechanics provided the atomistic and mechanistic underpinning to the older thermodynamic theory. But many fascinating questions in the border area of physics and philosophy arose out of these theories. What is the notion of probability involved? How are probabilities used in explanations in these theories? What explains why the fundamental probabilistic posits work as well as they do? How does the non-equilibrium theory that is asymmetrical in time arise out of an underlying time-symmetrical dynamics? What role does cosmology play in the explanations? Is thermodynamics really reducible to statistical mechanics? Finally, does our intuitive idea that time itself is asymmetrical, with past deeply unlike future, arise out of the physical asymmetries studied in this theory? The primary text will be L. Sklar, Physics and Chance.