Here we may observe that the obscure and mysterious concept of first matter whose acquaintance we made when we studied the notion of individual nature is that of a pure potentiality in order of substance, which can be any and every body and by itself is none. Potentiality and act divide between them the totality of created being , both in the order of substance and in the order of accidents. In other words, they are, like being itself, transcendental objects of thought which exceed or transcend every limitation of class or category, and include all created things. This is evident. For , since existence is an act ,potentiality can only exist in beings which are in some other respect in act.
Nothing is educed from potentiality to act except by some being in act .
It is plainly impossible that that which is in potentiality, that which is capable of having a determination or a perfection but does not have it , should give to itself what it lacks, so far as it does not possess it, that is to say, so far as it is in potentiality. A consequence of the preceding axiom. For it is evident that every act which at the same time completes and specifically determines a potentiality must belong to the order of that potentiality. The activity of thought, for example, belongs to the order of accident like the faculty itself from which it proceeds and which is in potentiality to that activity. For example , a living organism is a unit of itself, whereas a machine or a house is an accidental unit.