Thales, Anaximander, Anaximenes, Hericlitus, Plato, Aristotle...
the foundation of Western metaphyics...
I didn't mention Parmenides, but his notion that "Thinking is Being" certainly helped Plato...
Carl Sagan talks about some of the most important contributions, to science, that Anaximander, Democritus, Empedocles made. This clip is from Carl Sagan's Cosmos...