Philosophy is the study of the fundamental nature of knowledge, reality, and existence. Atheism is the lack of belief of the existence of a deity. Now while most Atheists will use the stance claiming no one is born with a belief in a deity, (which I would agree) therefore they don't have the burden of proof. Fair enough, however, at some point in our lives we reach the fork in the road to either maintain on the course of not believing or believing. Therefore, whether or not you would like to admit it, Atheism is a stance. It is not a study.