This is one of those unanswerable questions. I myself struggled over this
question at earlier points in my life. Philosophers have certainly
struggled with this question as well.

Although I cannot give a totally satisfactory answer to your question, God
himself provided a hint of an answer in Exodus 3:13,14. When Moses asked
God what his name was, he replied “I AM.” In saying this, God was
describing himself as the eternal self-existent being. Jesus gave a
similar answer when asked about when he was born. He said in John 8:58,
“before Abraham was born, I AM.” Notice, Jesus did not say “before Abraham
was born, I was.” It is no accident that he said “I AM.” Jesus claims
here, as did God in Exodus 3 that he is not defined by time. Jesus is
saying that he pre-existed all of creation. When God created the universe,
he also created time itself. There was no time outside of God’s creation.
By the way, physicists would agree with this contention. According to the
most common interpretation of the Big Bang model, not only was space
created in the Big Bang, but time itself also was “started.” When you ask
who created God, you use a human perspective which includes time. Where
there is no time, there is no creation. Please forgive me for being
abstract here, but that is the nature of the question you asked.

The Catholic theologian Thomas Aquinas addressed this question back in the
13th century. He was dealing with the concept of causality. He noted that
everything which happens in the natural universe has a cause. He also
noted that there had to be an initial cause of the first things. He
defined God as the initial causer of all things. God is “the uncaused
cause,” according to Thomas Aquinas. Although this is clearly a very
abstract definition and proof of God, I believe it remains valid today.

Philosophers of science come up against the ultimate cause problem as
well. For example you could ask why objects fall. They might explain that
gravity is the cause of objects falling. You could then ask the scientist
why gravity exists. They might explain that all objects with mass produce
gravitons, or gravity particles, which produce the attractive force. You
might proceed to ask why all objects with mass produce gravitons. The
scientist might get real abstract on you and begin discussing super string
theory or whatever. You could then ask a why question about strings. At
some point, the scientist will have to hold up his or her hands and just
say “that’s just the way it is.” Or, if the scientist is not an atheist,
he or she will say “God made it that way.”

I apologize for giving you an answer which probably raises more questions
than it solves, but that is the nature of the universe we live in. God is,
by definition, the uncaused cause. God is that thing which stands outside
our own universe and reality as the ultimate creator. God, by definition,
was not created, at least by the definition of creation or cause/effect as
it works in our reality. Bottom line, God exists. We have more than
sufficient evidence of God in nature, in the Bible and so forth, but in
the end, God is who he is. To use his own words, I AM.

John Oakes, PhD