If a man is, let us say, a Master of Arts, the formal principle, whereby he is such, is the degree itself; the efficient principle is the authority of the University which conferred the degree; while the man, on whom it is conferred, is the matter. This form is not substantial, but accidental: the man would be a man without it. But without his soul he would not be a man.

Of God and His Creatures: 2.68