As an a-theist, I lack a belief in god. Now, I can tell you that I'm pretty sure that Thor and the tribal war god Jehovah do not exist as well. As to other gods, I have no reason to suspect that they exist, but if you have reasonable evidence of it, lay it on me.
http://en.wikipedia.org/wiki/Atheist
Atheism is the state either of being without theistic beliefs, or of actively disbelieving in the existence of deities. In antiquity, Epicureanism incorporated aspects of atheism, but it disappeared from the philosophy of the Greek and Roman traditions as Christianity gained influence. During the Age of Enlightenment, the concept of atheism re-emerged as an accusation against those who questioned the religious status quo, but by the late 18th century it had become the philosophical position of a growing minority. By the 20th century, atheism had become the most common position among scientists, rationalists, and humanists (60.7 percent of U.S. general scientists and 93 percent of N.A.S. top scientists expressing disbelief or doubt, Nature 386:435-436 [1] (
http://www.nature.com/cgi-taf/DynaPa...t_filetype=pdf)).