First off, lets divide up atheists into two groups, strong atheists, and agnostics. It is important to show the differences between the two. Atheism has not really been a big player in the world until the eighteenth century when people wished to rise above the oppressive authority of the government and the church. But at the time, there was no big hubbub about it. Even Newton, a great scientist, published more articles about God than physics.
Atheism gained major fuel after Sigmund Freud made some comments about God. Today, prominent scientists like Richard Dawkins argue against God. He has several arguments. First, he claims, there is no need for God, as evolution accounts for all of life. Although this argument does prove that God did not magically make all living organisms, it does not disprove the idea that God worked out His creative plan through evolution. His second argument is that religion is irrational. I find this interesting because Dawkins claims that science demands atheism, but this goes beyond the evidence. If God is outside of nature, you cannot use science to prove or disprove God. Also, his definition of faith is flawed: blind trust in the absence of evidence. This does not fully encapsulate faith. Surely, arguments by CS Lewis and Thomas Aquinas proves that serious thinkers can intensely believe in God. Finally, he argues about all the bad created by religion. As I already mentioned, however, despite the evil, have not great things been done? Also, how do you pin that on God; is it not humans being imperfect containers for God and Moral Law?
Agnosticism is the belief that knowledge on God’s existence cannot be achieved. Note that agnosticism can, but does not need to be, a cop out. It should only be affirmed after a full consideration for and against the existence of God, and just about everyone who considers themselves agnostics do not do this. Science cannot be used to justify discounting the great religions of the world, which rest upon history, moral philosophy, and the evidence of human altruism. It is very deceitful and vain to say that you know for sure one way or another, as even people of great faith had doubts, but saying you know that God does not exist is just as wrong.