The reference point for God’s existence is His Fatherhood not His essence – 4

“The name of that which has no beginning is the Father, and of the Beginning the Son, and of that which is with the Beginning, the Holy Ghost, and the three have one Nature— God. And the union is the Father from Whom and to Whom the order of Persons runs its course, not so as to be confounded, but so as to be possessed, without distinction of time, of will, or of power” (Gregory of Nazianzus, Orationes 42:15).