 John Earman’s Primer on Determinism (1986) remains the richest storehouse of information on the truth or falsity of determinism in various physical theories, from classical mechanics to quantum mechanics and general relativity. (See also his recent update on the subject, “Aspects of Determinism in Modern Physics” (2007)). Here I will give only a brief discussion of some key issues, referring the reader to Earman (1986) and other resources for more detail. Figuring out whether well-established theories are deterministic or not (or to what extent, if they fall only a bit short) does not do much to help us know whether our world is really governed by deterministic laws; all our current best theories, including General Relativity and the Standard Model of particle physics, are too flawed and ill-understood to be mistaken for anything close to a Final Theory. Nevertheless, as Earman stressed, the exploration is very valuable because of the way it enriches our understanding of the richness and complexity of determinism.