Epicurus

He taught that pleasure and pain are the measures of what is good and evil, that death is the end of the body and the soul and should therefore not be feared, that the gods do not reward or punish humans, that the universe is infinite and eternal, and that events in the world are ultimately based on the motions and interactions of atoms moving in empty space.

Epicurus is a key figure in the development of science and the scientific method because of his insistence that nothing should be believed except that which was tested through direct observation and logical deduction.

http://en.wikipedia.org/wiki/Epicurus