Although there can be no doubt regarding the centrality of the concept of freedom in Kant's thought, there is considerable disagreement concerning its proper interpretation and evaluation. The evaluative problem stems largely from Kant's insistence that freedom involves a transcendental or non-empirical component, which requires the resources of transcendental idealism in order to be reconciled with the “causality of nature.” There is also, however, a significant interpretive problem posed by the number of different conceptions of freedom to which Kant refers. In addition to “outer freedom” or freedom of action, and a relative, empirically accessible or “psychological” concept of freedom, which admits of degrees, Kant distinguishes between transcendental and practical freedom, both of which seem to involve indeterminism in the sense of an independence from determination by antecedent causes. Moreover, within this sphere he conceives of freedom as both absolute spontaneity (negative freedom), which is a condition of rational agency as such, and as autonomy (positive freedom), which is a condition of the appropriate moral motivation (acting from duty alone).

Given this complexity, the present discussion must be highly selective. Specifically, it will focus initially on the nature of and relation between freedom as spontaneity and as autonomy. But since both of these senses of freedom affirm (albeit in different ways) an independence from natural causality, this necessitates a consideration of the relationship between freedom (in both senses) and transcendental idealism. And to situate Kant’s views in their historical context, I shall frame the discussion with a brief account of the treatment of free will by some of his predecessors, on the one hand, and his idealistic successors, on the other.