Augustine on the Trinity

There are the Father, the Son, and the Holy Spirit, and each is God, and at the same time all are one God; and each of them is a full substance, and at the same time all are one substance.  The Father is neither the Son nor the Holy Spirit; the Son is neither the Father nor the Holy Spirit; the Holy Spirit is neither the Father nor the Son.  But the Father is the Father uniquely; the Son is the Son uniquely; and the Holy Spirit is the Holy Spirit uniquely.  All three have the same eternity, the same immutability, the same majesty, and the same power.