Re:Dawkins may may a renowned evolutionary biologi (Score 3, Insightful)

It's because of Occam's razor. Theism posits that a God or Gods exist(s). However, observable evidence doesn't necessitate that one exist; that is, a God is an 'extra', if you will, there's no phenomena that cannot be explained without the existence of a God. As such, the principle of Occam's razor - do not make theories more complicated than necessary - eliminates the existence of a God, because the world is simpler without one. This leaves atheism as the remaining scientific theory. Another way of thinking about this is that all parts of scientific thought have doubt inherently as a part of them, not just ones surrounding God. So, atheism and agnosticism are essentially equivalent - few atheists would argue that they can prove that there is no God.