accordingly, had not drawn the necessary distinction between things as objects of experience and things as they are in themselves. The principle of causality, and, by consequence, the mechanism of nature as determined by causality, would then have absolute validity in relation to all things as efficient causes. I should then be unable to assert, with regard to one and the same being, e.g., the human soul, that its will is _free_, and yet, at the same time, subject to natural necessity, that is, _not free_, without falling into a palpable contradiction, for in both propositions I should take the soul in _the same signification_, as a thing in general, as a thing in itself—as, without previous criticism, I could not but take it. Suppose now, on the other hand, that we _have_ undertaken this criticism, and have learnt that an object may be taken in _two senses_, first, as a phenomenon, secondly, as a thing in itself; and that, according to the deduction of the conceptions of the understanding, the principle of causality has reference only to things in the first sense. We then see how it does not involve any contradiction to assert, on the one hand, that the will, in the phenomenal sphere—in visible action—is necessarily obedient to the law of nature, and, in so far, _not free;_ and, on the other hand, that, as belonging to a thing in itself, it is not subject to that law, and, accordingly, is _free_. Now, it is true that I cannot, by means of speculative reason, and still less by empirical observation, _cognize_ my soul as a thing in itself and consequently, cannot cognize liberty as the property of a being to which I ascribe effects in the world of sense. For, to do so, I must cognize this being as existing, and yet not in time, which—since I cannot support my conception by any intuition—is impossible. At the same time, while I cannot _cognize_, I can quite well _think_ freedom, that is to say, my representation of it involves at least no contradiction, if we bear in mind the critical distinction of the two modes of representation (the sensible and the intellectual) and the consequent limitation of the conceptions of the pure understanding and of the principles which flow from them. Suppose now that morality necessarily presupposed liberty, in the strictest sense, as a property of our will; suppose that reason contained certain practical, original principles _à priori_, which were absolutely impossible without this presupposition; and suppose, at the same time, that speculative reason had proved that liberty was incapable of being thought at all. It would then follow that the moral presupposition must give way to the speculative affirmation, the opposite of which involves an obvious contradiction, and that _liberty_ and, with it, morality must yield to the _mechanism of nature;_ for the negation of morality involves no contradiction, except on the presupposition of liberty. Now morality