Four Hundred Texts on Love (Fourth Century) 4

6.  Some say that the created order has coexisted with God from eternity; but this is impossible. For how can things which are limited in every way coexist from eternity with Him who is altogether infinite? Or how are they really creations if they are coeternal with the Creator? This notion is drawn from the pagan Greek philosophers, who claim that God is in no way the creator of being but only of qualities. We, however, who know almighty God, say that He is the creator not only of qualities but also of the being of created things. If this is so, created things have not coexisted with God from eternity.

We are not eternal beings. There was a time when we did not exist. There was a time when all that was did not exist. The idea that we are somehow naturally eternal seeps into Christianity from various sources today, even. We see evidence of that in various ways, but not least in Christians who also claim belief in the transmigration of souls or reincarnation.