Socrates (470 – 399 B.C.)

Protagoras (480 – 411 B.C.)

Democritus (460 – 370 B.C.)

Anaxagoras (495 – 428 B.C.)

Empedocles (495 – 435 B.C.)

Heraclitus (550 – 480 B. C.)

Parmenides (540 – 480 B. C.)