I see no logical or rational reason to believe in any kind of creator deity. Not only is there no solid evidence of any kind to support the existence of God (faith is, essentially, belief in spite of a complete absence of evidence) but the existence of an omnipotent, omniscient, omnipresent designer raises more questions that it answers.
For me, the clincher is this: if it is highly improbable that our universe, consisting of countless stars and planets in at least 100 billion galaxies and infinitely expanding, came to be from nothing (or more accurately from the point-singularity event we call the Big Bang), how much more improbable is the supremely complex being supposed to have designed it? The existence of a God at the Beginning begs the question “who created God?” which leads us to an infinite regress that is inescapable.
That initial spark of creation (which the Large Hadron Collider attempts to emulate) was a single, simple event that had to only happen once. One-off events are far more probable if simple than if complex, tipping the odds distinctly against God who (to use the term of “Intelligent Design Theorists”) is of an irreducible complexity almost beyond comprehension. Darwinian natural selection shows us how complex processes and beings can gradually emerge from simplicity, and leads us to seek out simplicity in origins, thereby near enough ruling out God.
Although we cannot completely disprove God’s existence, this is irrelevant as we can likewise not disprove Thor, Zeus, Santa, the Easter Bunny, or any other creation of myth/fiction. We can, however, judge that his existence is so improbable that he almost certainly does not exist. We do not “know” there is no God as Carl Jung “knows” there is one, as atheism is not a faith position, but the shades of probability and reason lead us to lean strongly towards that position.