Recently, there have been attempts to interpret Kant's philosophical insights into the problem of free will in light of contemporary compatibilist theory. Such attempts typically underplay the importance of Kant's  transcendental idealism. This thesis argues that the fundamental tenets of transcendental idealism are integral to a proper interpretation of the problem of free will, as Kant saw it, and to the manner in which Kant achieves a resolution to the problem. Of particular relevance, is Kant's contention that natural causation and freedom cannot both be possible without appealing to the transcendental distinction between appearances and things in
themselves. Since this distinction is the defining feature of transcendental idealism, I argue that the free will discussion of the third antinomy cannot be properly rendered unless it is interpreted from within the framework of transcendental idealism. Thus, this thesis offers an interpretation of transcendental idealism, an account of the interconnectedness of transcendental idealism and the third antinomy, and demonstrates the failure by  contemporary compatibilist theory to capture the essence of Kant's thought regarding the issue of free will.