The second analogy is the single argument intended both to replace the rationalists' fallacious derivation of the principle of sufficient reason from laws of logic alone and to refute Hume's skepticism that causal connections among distinct states of affairs can be known by human thought at all. Kant's rejection of a merely logical proof for the principle of sufficient reason was evident by the early 1760s, although even before then he had already pressed against Leibniz the argument that the principle entailed rather than precluded the genuine, causal action of one substance on another. Kant's obsession with Hume's attack on causation, of course, is manifest in his famous statement that it was this which first awoke him from his dogmatic slumber, and indeed that the Critique of Pure Reason itself was the result of nothing less than his attempt to put Hume's problem in its widest possible form (Prolegomena, 4:260–1). But the centrality of Hume's problem to Kant's thought is even more than usually evident in this passage from the Metaphysik Volckmann, which immediately precedes Kant's statement of the transcendental deduction in those revealing lectures: