In recent history, many philosophers have brought before the public their own cases against religion. I plan to present you with some of those arguments, as well as some of my own reasons not to believe.

Allow me to present you with one piece of evidence, science, our most valuable key to knowledge of the universe, being the first. It has been proven that human beings and modern chimps are almost genetically identical to each other and that we share a common ancestor. It has also been found transitional fossils of the primate-human transition.

We can also look at one of the most powerful arguments creationists used in pre Darwinian times, intelligent design.  This argument was turned around by Darwin himself to show that the universe is not perfect.  One piece of evidence often invoked by creationists is the human eye. They tell us this complex organ could not have evolved by chance. I disagree, if we take a moment to look at the human eye, we find that it is not perfect. One of the flaws we find is the location of blood vessel in the eye, they are in front of the optical nerves, thus, when a person looks into a bright light, or sometimes, even the blue sky, they see black spots. An intelligent engineer would have noticed such an obvious flaw. This flaw is not present in cephalopods, such as squids and octopuses. We can come to one of three conclusions from this observation:

1:  god didn't design the thing

2:  god is pretty sloppy and therefore undeserving of our worship

3:  god likes squids a lot more than humans

Another argument we can use are our available statistics.  It has been shown an inverse relationship in the amount of human knowledge and the amount of credibility we give to god.  The more we know the less we attribute to god.

Geology also, through the proof of an old earth, discredits many religion's creation theories, which credit the earth as being a few thousand years old.

We can also disregard the belief in god for the same reason we do not believe in other ridiculous things.  Why is it that no logically thinking person believes in Pegasus?  They cannot be disproved, to do so would require a universal search, but to believe in them would break, not only a few rules of everything we know about anatomical evolution, but also, aerodynamics.

WE can also examine religious hatred.  Many of the rules are suppressive of human instincts.  If a god created these instincts, should they not be nurtured?  Certain rules are needed to prevent anarchy in society, but the government should not try to "save" its people. Why should not a person be able to solicit prostitution? In this society, a woman can rent her body for nine months to couple wishing to have a baby, why not a few hours or less. It is forced morality in a society of supposedly enlightened people. We certainly don't need that.

In a society where a woman is harassed for making a choice about her own body, is forced morality even a sane choice. And, if it is, should we be using logic from a book whose most moral characters were guilty of genocide, rape, murder, and blasphemy against their own god. I think not.
This is not meant to be a condonement for atheism. But my reasons not to believe in a theistic deity. Be your own god. Ave Satanas, Ave Thine Self