Conclusion
The conclusion explains why the price for the architectonic unity of the initially separate systems of nature and freedom is a transcendental theology which implicitly commits reason to metaphysical assumptions about the order of nature which its critical part has explicitly ruled out. This is useful to understand why Kant later retracted the defence of physico-theology and converted it to ethical theology in the Critique of the Power of Judgment, a text where the problem of purposiveness is carefully distinguished from the use of ideas, and where we find a separate faculty responsible for the use of purposive principles: the faculty of judgment. Understanding the demand for systematic unity and its execution in the Architectonic of Pure Reason is crucial to make sense both of how that project developed in the first Critique, and of the need to return to a reconfiguration of the system in subsequent works.