This book deals with foundational issues in the theory of the nature of action, the intentionality of action, the compatibility of freedom of action with determinism, and the explantion of action. Ginet's is a volitional view: that every action has as its core a 'simple' mental action. He develops a sophisticated account of the individuation of actions and also propounds a challenging version of the view that freedom of action is incompatible with determinism.