Metaphysical Voluntarism

What does it mean for “will” to be a cosmic force or first principle a la Schopenhauer or Nietzsche? I’m just having some trouble intuiting a metaphysical system centered entirely on what seems to be an animal phenomenon (conscious or sub-conscious desire).

“[…]this, my Dionysian world of the eternally self-creating, the eternally self-destroying, this mystery world of the twofold voluptuous delight, my “beyond good and evil,” without goal, unless the joy of the circle is itself a goal; without will, unless a ring feels good will toward itself[…]” - Nietzsche, Will to Power 1067

How is this metaphysical?

The “will in nature” of Schopenhauer is that which motivates all matter. In the simplest sense, it’s the force that attracts matter to matter (ie, gravity), so it there strives for unity. As you move up the “grades” of forms of matter, the forces becomes more complex, with the most complex motivations of all being in human beings (what drives a man?, etc) Thus, the same thing causes a man to chase a buffalo as causes a stone to fall off a roof.

This leads to a nice quote from Spinoza: if a stone could speak, it would say it went straight downwards of its own free will.