This chapter investigates how Kant influences Nietzsche's metaphysics. By highlighting the historical context informing Nietzsche's concern with the metaphysical status of force in his will to power thesis it underscores the particular Kantian lens through which Nietzsche grapples with the metaphysical problem of the reality of causal powers.

In his articulation of the will to power thesis in Beyond Good and Evil Nietzsche describes the ultimate constituents of reality in causal terms, arguing that ‘effective’ causes have an intrinsic nature, capturing the ‘world as it is seen from the inside’. Whilst Nietzsche's claim in this passage that ‘I do not mean the material world as a delusion … (in the Berkeleian or Schopenhauerian sense)’ makes it clear that he intends his will to power thesis to dissociate him from Schopenhauer, what is not immediately evident is that his explicit identification of force with efficient causality entails a rejection of Schopenhauer's criticism of Kant's treatment of the concept of force.

According to Schopenhauer, the empirical world, or the world as representation, conforms to a priori principles of sufficient reason. Scientific causation, as one form of the principle of sufficient reason, he contends, captures the relational character of empirical phenomena but not their intrinsic natures. Distinguishing natural force from causality, he argues that forces of nature are direct objectifications of the Will in its essence (‘Ideas’) and not yet individuated by the principle of sufficient reason. Natural force, therefore, in Schopenhauer's view, is non-causal, non-temporal and non-spatial, although it manifests itself in those forms at the empirical level.