Generally speaking, Naturalism is a philosophical system which holds that everything can be explained by means of natural causes. Naturalism can be summed up with Carl Sagan's infamous quote that "The Cosmos is all that is, or ever was, or ever will be." [1] Naturalism denies the existence of the supernatural and is thus opposed to supernaturalism. It is held by virtually all atheists. Modern day proponents of naturalism include Richard Carrier, Keith Parsons, and Michael Martin.