13. Further, they must explain in what sense they hold that Matter tends to slip away from its form [the Idea]. Can we conceive it stealing out from stones and rocks or whatever else envelops it?
And of course they cannot pretend that Matter in some cases rebels and sometimes not. For if once it makes away of its own will, why should it not always escape? If it is fixed despite itself, it must be enveloped by some Ideal-Form for good and all. This, however, leaves still the question why a given portion of Matter does not remain constant to any one given form: the reason lies mainly in the fact that the Ideas are constantly passing into it.
In what sense, then, is it said to elude form?
By very nature and for ever?
But does not this precisely mean that it never ceases to be itself, in other words that its one form is an invincible formlessness? In no other sense has Plato’s dictum any value to those that invoke it.
Matter [we read] is “the receptacle and nurse of all generation.”
Now if Matter is such a receptacle and nurse, all generation is distinct from it; and since all the changeable lies in the realm of generation, Matter, existing before all generation, must exist before all change.