This chapter presents a unified reading of the metaphysical, moral, and political parts of Kant’s account of human free agency: the transcendental idea of a spontaneous causal power, the normative idea of acting under reason’s highest principle, and the political idea of acting for oneself rather than being under the control of another agent. It argues that Kant understands our freedom as a involving a spontaneous causal power that is engaged under the non-optional commitment to reason’s highest principle, and that this principle further commits us to realizing the conditions under which we can all act for ourselves. It evaluates each part of his position in relation to the idea of robust alternative possibilities, and argue that his account requires what is now called leeway freedom. The chapter argues against two main reasons that have been taken as reasons for thinking that his account does not require leeway: the idea that God lacks leeway and the idea that freedom is not lawless. Kant sees moral blame as requiring the possibility that you could have acted other than you did, and sees our recognition of moral claims as involving the awareness that we can act on them or not act on them. The chapter argues that this requires that at the point of action more than one course of action is available to the agent and therefore that action is not a nomologically determined function of previous states of the universe. Rather, we have the causal power to bring about one thing or another, though we cannot positively characterize this causal power in metaphysical or theoretical terms. Our freedom is understood positively in terms of the idea of acting under reason’s highest principle, and we act under reason’s highest principle both when we act in accordance with what it requires and when we act against this.