Marsilio Ficino’s Platonic Theology, Volume II

13The following third argument persuades us of the same conclusion. All motions are these: alteration, generation, corruption, increase, decrease, condensation, rarefaction, and progression. Does a body move itself by alteration? Not at all. If it is to heat itself, it must possess the heat that it gives itself. Yet it must also not possess that heat if it is to receive it, for no one receives what he already possesses. Thus, insofar as the body heats, it is already hot; insofar as it is heated, it is not yet hot. It is plainly absurd to say that the same thing both has and does not have something at once. Perhaps someone will say that water possesses a certain coldness virtually, which it retains even after fire has heated it, and through which, once removed from the fire, it returns again to coldness in act. The Platonists will reply in either of two ways. Either the water is cooled by external elements; or, if its actual quality—which approaches somewhat toward incorporeal nature—springs from an inward power productive of quality, and if that power approaches still nearer to incorporeal nature, it follows that such a power in turn springs from some substance that is wholly incorporeal. A substance of this kind will be the principle of motion in the body.

14No body, then, moves itself by alteration. Nor does a body generate itself. For whatever generates another gives being to what it generates. The begetter therefore possesses the being it gives the begotten, whereas what is generated receives from elsewhere the being it does not itself possess. Nothing, then, can give itself being; it would both possess being and not possess it at once. And since the begetter precedes the begotten, whatever within finite nature were both its own begetter and its own offspring would be at once prior and posterior to itself—something no one would suppose possible in a finite nature. Nor, again, does a body corrupt itself. For every thing generates its offspring from its own nature and therefore brings forth what accords with it, not what is contrary to it. It follows that the natural impulse of each thing, which is a kind of offspring of its essence and of its very being, does not rise against essence and being. No thing, therefore, is led by its own impulse toward non-being—least of all its own non-being, but not that of anything else either. Indeed, since the striving of each thing sets out to preserve itself, it will not be turned in the contrary direction.