And as the undefinable essence of the force moving the heavenly bodies, the undefinable essence of the forces of heat and electricity, or of chemical affinity, or of the vital force, forms the content of astronomy, physics, chemistry, botany, zoology, and so on, just in the same way does the force of free will form the content of history. But just as the subject of every science is the manifestation of this unknown essence of life while that essence itself can only be the subject of metaphysics, even the manifestation of the force of free will in human beings in space, in time, and in dependence on cause forms the subject of history, while free will itself is the subject of metaphysics.
In the experimental sciences what we know we call the laws of inevitability, what is unknown to us we call vital force. Vital force is only an expression for the unknown remainder over and above what we know of the essence of life.
So also in history what is known to us we call laws of inevitability, what is unknown we call free will.