Nam velut amores corporum momenta sunt ponderum, sive deorsum gravitate, sive sursum levitate nitantur: ita enim corpus pondere, sicut animus amore fertur quocunque fertur_” (De Civ. Dei, xi. 28). It ought further to be mentioned that Euler saw that the inner nature of gravitation must ultimately be referred to an “inclination and desire” (thus will) peculiar to material bodies (in the 68th letter to the Princess). Indeed, it is just this that makes him averse to the conception of gravitation as it existed for Newton, and he is inclined to try a modification of it in accordance with the earlier Cartesian theory, and so to derive gravitation from the impact of an ether upon the bodies, as being “more rational and more suitable for persons who like clear and intelligible principles.” He wishes to banish attraction from physics as a _qualitas occulta_. This is only in keeping with the dead view of nature which prevailed at Euler’s time as the correlative of the immaterial soul. It is only worth noticing because of its bearing upon the fundamental truth established by me, which even at that time this fine intellect saw glimmering in the distance. He hastened to turn in time, and then, in his anxiety at seeing all the prevalent fundamental views endangered, he sought safety in the old and already exploded absurdities. We know that _multiplicity_ in general is necessarily conditioned by space and time, and is only thinkable in them. In this respect they are called the _principium individuationis_. But we have found that space and time are forms of the principle of sufficient reason. In this principle all our knowledge _a priori_ is expressed, but, as we showed above, this _a priori_ knowledge, as such, only applies to the knowableness of things, not to the things themselves, _i.e._, it is only our form of knowledge, it is not a property of the thing-in-itself. The thing-in-itself is, as such, free from all forms of knowledge, even the most universal, that of being an object for the subject. In other words, the thing-in-itself is something altogether different from the idea. If, now, this thing-in-itself is _the will_, as I believe I have fully and convincingly proved it to be, then, regarded as such and apart from its manifestation, it lies outside time and space, and therefore knows no multiplicity, and is consequently _one_. Yet, as I have said, it is not one in the sense in which an individual or a concept is one, but as something to which the condition of the possibility of multiplicity, the _principium individuationis_, is foreign. The multiplicity of things in space and time, which collectively constitute the objectification of will, does not affect the will itself, which remains indivisible notwithstanding it. It is not the case that, in some way or other, a smaller part of will is in the stone and a larger part in the man, for the relation of part and whole belongs exclusively to space, and has no longer any meaning when we go