Kant wrote two other books named "Critique": "Critique of the practical reason" (1788) and "Critique of the Judgement" (1790). In "Critique of the practical reason" Kant wrote about the problem of freedom and God. It was his main work of ethics. In "Critique of the Judgement" Kant wrote about beauty and teleology, or the problem if there was a purpose in general, if the world, a living creature had a reason to exist, and so on. In both books, Kant said we could not answer those problems, because they were concerned with "thing itself".