Full Idea
Nietzsche challenged belief in free will, on the ground that willl itself …is non-existent. The will is in truth nothing but a complex of sensations, as of power and resistance, and it is illusion to think of it as a basis for 'moral responsibility'.
Gist of Idea
Nietzsche said the will doesn't exist, so it can't ground moral responsibility
Source
report of Friedrich Nietzsche (Human, All Too Human [1878], 107) by Philippa Foot - Nietzsche's Immoralism p.153
Book Reference
Foot,Philippa: 'Moral Dilemmas' [OUP 2002], p.153
A Reaction
Modern neuroscience seems to support Nietzsche on this, though I will continue to use the concept of 'will' in philosophy, to mean the main brain events which normally combine in decision-making. That makes the will a process, not a entity.