166. (2) THESE THREE, FATHER, SON AND HOLY SPIRIT, ARE THREE ESSENTIALS OF ONE GOD, WHICH MAKE ONE, AS SOUL, BODY AND OPERATION MAKE ONE IN A MAN.
In everything there are general and particular essentials which together constitute one essence. The general essentials of a man are his soul, body and operation; and that these constitute one essence is evident from this fact that one exists from the other, and for the sake of the other, in a continuous series; for a man has his beginning from the soul, which is the very essence of the seed. It, moreover, not only initiates but also produces in its own order the parts of the body, and later the activities, or operations, which result from the co-operation of soul and body. Thus from the production of one from the other, and their interpenetration and conjunction, it is evident that these three are of one essence, and are therefore called three essentials.