The paper discusses Kant’s pre-critical ‘possibility proof’ for the existence of God against a background of recent reinterpretations of this argument, which point at Spinozist consequences for Kant’s conception of God that can follow from the ‘proof’ (O. Boehm, A. Chignell). I contend that, in the light of textual evidence, attributing a Spinozist conception of God to the pre-critical Kant would misrepresent his view. However, while he would never openly subscribe to Spinozism, Kant seems to be well aware, especially in the critical period, that the dogmatic metaphysics he endorsed before the ‘Copernican revolution’ was under a Spinozist ‘threat.’ In this paper I attempt to find out what the source of the ‘threat’ might be and I reach conclusion that the potential for Spinozism contained in Kant’s pre-critical metaphysics derives from his account of the divine grounding of possibilities, on some plausible accounts of grounding, and in particular from the incompatibility between his conception of spatial extension as one of the basic features of reality and the divine nature that is supposed to ‘ground’ the basic properties of reality and their consequences.