His eternality, perhaps more than anything else, sets God apart from us. His holiness refers not only to His purity but also to His otherness or transcendence—the sense in which He is different from us. One thing we human beings have in common is that we are creatures, who by nature are temporal. At the end of a person’s life, when he is buried, his grave is marked by a tombstone on which are inscribed his name and the dates of his birth and death. We live on this earth between those two dates: birth and death. There are no such dates for God.
People may argue that if every effect has a cause, then God must have a cause. They may therefore ask, What was there before God? But the eternal God is not an effect. There never was a time when He was not. God’s being is derived from nothing outside of Himself, nor is He dependent on anything outside of Himself. Nothing differentiates God from the creature more dramatically than this, because the creature, by definition, is dependent, contingent, and derived and lacks the power of being in and of himself. God requires nothing; He exists from all eternity.
Eternality goes in the other direction as well. There will never be a time in the future when God will cease to be. His being remains self-existent for all eternity. If anything exists, then something has always existed. If there ever was absolutely nothing, then nothing could possibly be now, because you cannot get something out of nothing. Conversely, if there is something now, then that in itself demonstrates that there always was something. And that which always is exists in and of itself. That is the One who has the power of being within Himself, the living God.