2. Supposing we accept this view and hold that, while things below the moon's orb have merely type-persistence, the celestial realm and all its several members possess individual eternity; it remains to show how this strict permanence of the individual identity- the actual item eternally unchangeable- can belong to what is certainly corporeal, seeing that bodily substance is characteristically a thing of flux.
The theory of bodily flux is held by Plato no less than by the other philosophers who have dealt with physical matters, and is applied not only to ordinary bodies but to those, also, of the heavenly sphere.
"How," he asks, "can these corporeal and visible entities continue eternally unchanged in identity?"- evidently agreeing, in this matter also, with Herakleitos who maintained that even the sun is perpetually coming anew into being. To Aristotle there would be no problem; it is only accepting his theories of a fifth-substance.
But to those who reject Aristotle's Quintessence and hold the material mass of the heavens to consist of the elements underlying the living things of this sphere, how is individual permanence possible? And the difficulty is still greater for the parts, for the sun and the heavenly bodies.
Every living thing is a combination of soul and body-kind: the celestial sphere, therefore, if it is to be everlasting as an individual entity must be so in virtue either of both these constituents or of one of them, by the combination of soul and body or by soul only or by body only.
Of course anyone that holds body to be incorruptible secures the desired permanence at once; no need, then, to call on a soul or on any perdurable conjunction to account for the continued maintenance of a living being.
But the case is different when one holds that body is, of itself, perishable and that Soul is the principle of permanence: this view obliges us to the proof that the character of body is not in itself fatal either to the coherence or to the lasting stability which are imperative: it must be shown that the two elements of the union envisaged are not inevitably hostile, but that on the contrary [in the heavens] even Matter must conduce to the scheme of the standing result.