"a substantial change--that is to say, a change in which one substance, made known to the understanding by its qualities, ceases to be what it was in the instant A, and becomes, in the instant B, another substance. In order that such a change should be possible, four things are necessary: namely,
- the thing that is changed;
- the term, or manner of being, or essence, that is induced in that which is changed;
- the active agent that produces the change, or accomplishes the existence of the new term, manner of being, or essence; and the motive, or reason why this latter acts.
.... A cube of wax is moulded by the hand into a sphere. The wax, as permanent substratum of the change of figure, is considered to be the matter, or material cause. The spherical figure supervening upon that of the cubical, is the induced formal cause. The moulder, or fashioner of the sphere, is the efficient cause. The final cause is to be sought for in the intention of the moulder. The substance of the wax remains throughout the entire process of the moulding. It is affected only accidentally by the operation. Consequently the example is one of accidental change, and gives us no more than an accidental formal cause."