  Kant develops his account of the nature of substance in greater detail in A New Elucidation of the First Principles of Metaphysical Cognition (1755). While the first two sections of this work undertake revisions of Wolff's principles of non-contradiction and sufficient reason, the third section argues for two substantive principles that are alleged to follow from the principle of sufficient (or rather, following Crusius, determining) reason, namely the principles of succession and coexistence. The main thrust of the principle of succession is directed against Leibnizian pre-established harmony, arguing that only causal connections between substances can bring about changes in their states. Kant's position appears to be designed to account primarily for changes of bodily states (with changes in mental states being parasitic upon them, as was explicitly asserted in the True Estimation). For he maintains that mutual changes of state require mutual interaction, where it is clear that changes in motion are precisely the kind of mutual change that he has in mind (since one body cannot move closer to another without the other body moving closer to it). The principle of coexistence then argues that harmonious causal interaction between otherwise isolated, independently existing substances is possible only by means of God's coordination (just as Leibniz thought was required for harmonious relations between the states of such substances).