"As far as we can reach, He Who Is, and God, are the special names of His Essence; and of these especially He Who Is, not only because when He spoke to Moses in the mount, and Moses asked what His Name was, this was what He called Himself, bidding him say to the people 'I Am has sent me' (Ex. 3:14), but also because we find that this Name is the more strictly appropriate."

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Can anyone be a father without beginning to be one? Yes, one who did not begin his existence. What begins to exist begins to be a father - God the Father did not begin at all. He is Father in the true sense, because He is not a son as well. Just as the Son is son in the true sense, because He is not a father as well. In our case, the word 'father' cannot be truly appropriate, because we must be fathers and sons.

— Gregory of Nazianzus