Critique of Practical Reason
The first Critique, "of Pure Reason", was a criticism of the pretensions of those who use pure theoretical reason, who claim to attain metaphysical truths beyond the ken of applied reasoning. The conclusion was that pure theoretical reason must be restrained, because it produces confused arguments when applied outside of its appropriate sphere. However, the "Critique of Practical Reason" is "not" a critique of "pure" practical reason, but rather a defense of it as being capable of grounding behavior superior to that grounded by desire-based practical reasoning. It is actually a critique, then, of the pretensions of "applied" practical reason. Pure practical reason must not be restrained, in fact, but cultivated.