Most people have heard of Socrates, Plato and Aristotle. However it is not so widly known that there is a whole area of philosophy called pre-socratic philosophy. This takes us back to the very beginings of greek philosophy and indeed of philosophy itself.
It begins with three philosophers by the names Thales, Anaxmander and Anaximenes. They lived in the 6th century BC, Thales believed that the essential nature of everything was watery, that is everything emerged out of water. Anaximenes however believed everything arose out of opposites with five being particulaly important. These three philosophers, as they are called, are important because they offer an alternative explanation to that which is used in religion or mythology. They attempt to reduce everything to a materialistic essence that can be observed and to some extent verified, and whereas a god requires a particular kind of interpriter or intermediary to say, as Thales said, "All is water" is to make a statement that at least in theory is within the experience of ordinary people. On the other hand these observations are culturaly conditioned, for example, in Egyptian mythology the world is often pictured surrounded by water, and fire as a creative and destructive principle is widespread.