“ The question of the possibility of freedom does indeed concern psychology; but, as it rests upon dialectical arguments of pure reason, its solution must engage the attention of transcendental philosophy. ”
 Immanuel Kant, Critique of Pure Reason (1791). copy citation

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“Here, too, we find it to be the case, as we generally found in the self-contradictions and perplexities of a reason which strives to pass the bounds of possible experience, that the problem is properly not physiological, but transcendental. The question of the possibility of freedom does indeed concern psychology; but, as it rests upon dialectical arguments of pure reason, its solution must engage the attention of transcendental philosophy. Before attempting this solution, a task which transcendental philosophy cannot decline, it will be advisable to make a remark with regard to its procedure in the settlement of the question.
If phenomena were things in themselves, and time and space forms of the existence of things, condition and conditioned would always be members of the same series; and thus would arise in the present case the antinomy common to all transcendental ideas—that their series is either too great or too small for the understanding.” source