As readers of Nietzsche know, he tinkered with a project for a book called
The Will to Power, but abandoned it well before he went mad. His enterprising sister published selections from his notebooks under that title as if it were his "unpublished masterpiece," creating no end of misunderstanding for many years.
Much moreso than "the superman" or "the eternal recurrence," the will to power has a good claim to be a central part of N's thought. A problem for his readers has been that, while being the anti-metaphysician
par excellence, N. has also been accused of making "will to power" into some kind of metaphysical substrate of reality. Besides being a rather odd error for N. of all people to make, this reading also relies heavily on the notebooks, tho not entirely so.
The will to power is best understood in terms of
interpretation, as may be seen from those who best exemplify it in N's view -- the creators of moral systems, those who invent and implement values for a society. N.b. that after he abandoned the
Will to Power project, his next notion was for a magnum opus called
The Revaluation of All Values (of which
The Antichrist was supposed to be vol. 1).
Reading in a
modern selection from the notebooks, I think I've identified some of what N. was up to with his "metaphysical" notions of will to power. Take what appears a troubling note from June-July 1885:
The triumphant concept of "force," with which our physicists have created God and the world, needs supplementing: it must be ascribed an inner world which I call "will to power," i.e. an insatiable craving to manifest power; or to employ, exercise power, as a creative drive, etc. The physicists cannot eliminate "action at a distance" from their principles, nor a force of repulsion (or attraction). There is no help for it: one must understand all motion, all "appearances," all "laws, as mere symptoms of inner events, and use the human analogy consistently to the end.
This "must" is, to say the least, spectacularly unconvincing. One would think N. would prefer to escape "the human analogy" altogether.
Leaving aside the very dubious grasp of even late 19th-c. science possessed by a prematurely retired professor of classical languages, I think what's up here is that N. (1) believes in a fundamentally a-human, value-free, indifferent cosmos, and (2) finds that belief utterly useless for the creator of values. True, the world is alien to human desires and fears and couldn't care less if we prosper or perish; but then, why should we let the truth distract us from the project of creating civilized humans? One "must" imagine nature in terms of "the human analogy" because anything else is boring to Nietzsche.
This rather cavalier dismissal of scientific thought is made more clear when we compare the above passage to a somewhat later notebook entry:
A force we cannot imagine (like the allegedly purely mechanical force of attraction and repulsion) is an empty phrase and must be refused rights of citizenship in science -- which wants to make the world imaginable to us, nothing more!
Again, this is a remarkably narrow notion of what "science" (presumably,
wissenschaft, which can mean more like "academic discipline" than a hard science) is properly concerned with. But again, N. is concerned with what the world means to humans, what we can imagine. I guess he would've had no use for the world of quantum mechanics, where we can use mathematics to make amazing predictions of real events, but at the cost that, quite plainly, we
cannot imagine what it is we are describing. (As Bohr said, whoever thinks he understands quantum physics, doesn't understand it.)
In short: N. did not "really think" that the world, or organic matter, was "made of" will to power; he simply thought that, inasmuch as thought's inseparable from interpretation (and thus from will to power), the question of what the world "is really made of" was simply not very interesting, and at worst, an invitation to nihilism ("atoms and the void"). Far better, in N.'s view, to believe a value-supporting falsehood about the world, than to pursue an ultimately nihilistic "will to truth" to the point of undoing our values and, therefore, ourselves.