Heraclitus of Ephesus (c.500 BCE): one of the pre-Socratic philosophers of ancient Greece.
Unfortunately, a great part of his work is lost, which makes it very difficult to reconstruct Heraclitus' ideas. It seems certain, however, that he thought that the basic principle of the universe was the logos, i.e. the fact that it was rationally organized and therefore understandable. Bipolar oppositions are one form of organization, but the sage understands that these oppositions are just aspects of one reality. Fire is the physical aspect of the perfect logos.