 Although Kant rejects the physiciotheological argument as a theoretical proof for God’s existence, he also sees in it a powerful expression of reason’s need to recognize in nature purposive unity and design (cf. A625/B651). In this, the physicotheological argument’s emphasis on the purposiveness and systematic unity of nature illuminates an assumption that Kant takes to be essential to our endeavors in the natural sciences. The essential role played by the assumption of purposive and systematic unity, and the role it plays in scientific inquiries, is taken up by Kant in the Appendix to the Transcendental Dialectic. To this topic we now turn.