In summary, the Three Cappadocians taught that
The one God-head subsists in three coequal, coeternal, coessential persons, and this truth is an incomprehensible mystery. There is communion of substance but distinction of personhood. This trinity is a perfect, inseparable, indivisible union, and the persons work together in all things. The unique distinguishing characteristics of the persons are as follows: the Father is unbegotten, the Son is begotten (generated), and the Holy Spirit is proceeding (spirated). The generation of the Son and the procession of the Holy Spirit are mysteries, however. While the persons are coequal and coeternal, the Father is in some sense the head and the origin.56