Parmenides (circa 515 B.C.) was one of the greatest members of the 
Eleatic school of philosophy. He developed a system of metaphysics 
from the Eleatic doctrines. Parmenides believed the existence of 
separate objects is mere illusion. True reality, according to him, could 
only be found in reason, not through the senses. His beliefs, along with 
those of Pythagoras, laid the groundwork for later Greek philosophy.