In the Appendix to the Dialectics of the Critique of Pure Reason Kant asserts that the purposive unity of things is the highest formal unity and that reason demands its pursuit. The pursuit of this unity leads immediately to the reintroduction of a “supreme intelligence” or archetypus intellectus as cause of the world and its unity and opens up new prospects of interpreting the world according to teleological laws. After spending half a lifetime – and a large part of the first Critique – getting God out of nature and criticizing the physico-theological proof of God’s existence and properties, Kant here seems to make completely unexpected concessions to theology. However the entire discussion of God as the source of the world and its unity is qualified by the characterization of God’s existence and activity as being “merely in the idea.” The figure of argument that Kant introduces here, but uses nowhere else in this terminology, nonetheless bares a strong resemblance to an argument that he later uses in the discussion of (objective) natural purpose in the Critique of Judgment. There, in a discussion of the purposive unity of the organism (and at various places in the Logic) Kant distinguishes between a “ground of cognition” (Erkenntnisgrund) and a real ground or cause.
This paper will pursue Kant’s treatment of the idea of God (and of natural purpose) as an instrument for knowledge about the world that apparently has no intended reference to a transcendent being (or a noumenal object). The comparison between the two types of purposive unity will be used better to understand the various roles of the designer in Kant’s doctrine of the unity of nature. In particular, the role of reason’s demand for unity in explaining the necessity attributed by Kant to various regulative principles in the Dialectics of the First Critique and in the analysis of teleological judgment in the Third Critique will be analyzed. The paper will then assess the consequences of the analysis of objective purposiveness and of the cognitive grounds of the unity of nature for the status and role of laws of nature whether mechanical or teleological.