In the first chapter of his Beyond Good and Evil, titled “On the Prejudices of the Philosophers”, Nietzsche critiques the philosophers in general, and Schopenhauer in particular, on the subject of the will (aphorism 19). He suggests that Schopenhauer not only considered the will something simple, like the philosophers in general, but even the only simple thing we know. In other words, he suggests that Schopenhauer considered the will the archê, like Democritus his “atom”.
And Nietzsche would not be Nietzsche if he left it at a rejection of that view; he immediately offers an alternative, saying that he considers the will “above all” something complex, and then proceeding to analyse this complex. In the course of his analysis, however, he contends that the will is “above all” the “affect of the command”. And this is where I’ll jump to a notebook entry of his, published in The Will to Power:
[size=95]“Willing” is not “desiring”, striving, demanding; it is distinguished from these by the affect of the command. [Source: WP 668, trans. Kaufmann, with my amendments.][/size]
I think this is where Nietzsche most fundamentally disagrees with Schopenhauer—inasmuch as Schopenhauer considered the will synonymous with desire, want, lack, need. I think here is to be found the main reason why Schopenhauer’s philosophy is pessimistic, and Nietzsche’s, the opposite!
Even in the very beginning of his philosophical career, this disagreement was already present. For though Nietzsche considered the world as we know it to be indeed characterised by becoming, lack, and woe, he proposed a most personal metaphysics according to which the world as we know it was really an imaginary self-fragmentation on the part of something he called “the primordial One”, which was characterised by being, overfullness, and overjoyedness. As William Blake said, excess of joy weeps; and according to the early Nietzsche, it was a primordial excess of joy that was weeping forth this vale of tears.
For my summary of Nietzsche’s early metaphysics, see http://www.ilovephilosophy.com/viewtopic.php?p=2133051#p2133051.
Also here on ILP (though in the Rant House, which isn’t accessible to non-members), I have distinguished between desire for pleasure and desire as pleasure. But how can desire be pleasurable? Or, in other words, what is it that makes pleasurable desire pleasurable? I contend that it is the affect of the command. So it’s not actually desiring which is pleasurable, but willing; not Schopenhauerian willing, but Nietzschean willing. What Nietzsche at the end of his Twilight of the Idols calls “the eternal joy of becoming” is the joy of commanding, the affect of the command.