Full Idea
One needed God as an unconditional sanction, as a 'categorical imperative'; or, if one believed in the authority of reason, one needed a metaphysic of unity, by virtue of which this was logical.
Gist of Idea
The categorical imperative needs either God behind it, or a metaphysic of the unity of reason
Source
Friedrich Nietzsche (The Will to Power (notebooks) [1888], §275)
Book Reference
Nietzsche,Friedrich: 'The Will to Power', ed/tr. Kaufmann,W /Hollingdate,R [Vintage 1968], p.157
A Reaction
I am not sure what a 'metaphysic of unity' is, but this still captures the problem with Kant. The categorical imperative is purely formal, and will justify consistent principles of pain and destruction, without some value to get it off the ground.