God revealed himself to Moses as, "I am who am", which is sometimes rendered "Yahweh".  This name or self-definition of God has no precedent and has provided theologians, philosophers, and ordinary Christians much to ponder on in the more than three thousand years since Moses heard these words.  A number of Church Fathers and medieval writers wrote treatises on the Holy Trinity in which they expounded on these words.  St. Hilary of Poitiers (d. 367), a bishop in Gaul, was one of the first to do so.  He had been brought up in a pagan family and had come to Christianity through a broad range of study, including the reading of the Holy Scriptures.  He begins his book by speaking about his search for God.  Finding various pagan philosophical ideas about God unconvincing, he finally came to the Scriptures: 

"Therefore, considering these things and many others, I came upon those books of the Hebrew religion said to have been written by Moses and the Prophets.  They contained the words of God the Creator, testifying of himself: 'I am who am' (Exodus 3, 14).  And again: 'You shall say to the children of Israel: The One who is, sent me to you.'  I wholly admired such an absolute definition of God, which spoke the incomprehensible knowledge of the divine nature in a phrase most adapted for human understanding.  [It means that] no property is known to belong to God that is greater than existence, for existence neither ceases nor begins to be.  But since he himself is eternal existence, with the power of incorruptible happiness, he neither could nor can cease to be.  Therefore, whatever is divine is subject neither to non-existence nor to a beginning.  And since the eternity of God is in no way separable from himself, it was worthy for him to show this one characteristic, that 'he is', as a declaration of his incorruptible eternity."