 Kant criticized arguments for God’s existence (presumably brought to his attention through Wolff’s Theologia Naturalis) that departed from the premise that the concept of God is noncontradictory as fallacious hyperrationalism. The Leibnizian argument rested, he thought, on the uncritical notion that every noncontradictory concept was a possible thing (20:302), though it is unclear why he attacks this claim in particular. Kant did not think any rationalistic proofs for the existence of God actually worked, though, at least before the mauling it received at the hands of Hume, he considered the physico-theological argument the best available. He noted perceptively the arbitrariness of merging into one theological idea a creator and a judge. Without revelation, we might be drawn to the ideas of a creator God, but why would we suppose this same being to have the power of reward and punishment after death? Taking a page from Locke, Kant decided that, since the existence of God was unknowable, philosophical effort should be directed to the idea of God, especially the separate functions that the idea of God plays in regulating our moral conduct ( judge concept) and our mode of address to the problems of form and function in the organic realm (creator concept). The distinction between the realm of grace and the realm of nature, one standing under moral laws of reward and punishment, the other under natural laws, Kant describes as a “practically necessary idea of reason” (KRV A 812 f/B 840). We conceive the world both as a community of active spirits, willing and representing, and as an aggregate of objects in mechanical interplay and shift perspectives as needed.