Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means (Bertrand Russell, 1929 Lecture)." - My talk develops an account of laws and chances that is based on David Lewis' Best Systems Account and argues that I is superior to frequency, propensity, and purely subjective accounts. I show how this account applies to indeterministic laws and also allows for objective physical probabilities that are compatible with deterministic dynamical laws. This plies to classical statistical mechanics and Bohmian mechanics. I show how this account explains why objective probabilities guide credences and thus supports Lewis remark that he can "see dimly but well enough why chance is a guide to credence."
