Thales -624 ’Äî -547

The father of Western Philosophy, or Science...

Pythagoras -582 ’Äî -497

Almost all belief in the usefulness (or reality, for the extremists) of pure form and mathematics originates with Pythagoras and his followers.

Heraclitus -540 ’Äî -480

Accommodates the sensory information that suggests that change is everywhere. See more in HW.

Parmenides -510 ’Äî 0

One of those from Elea, in Italy (the "Eleatics"). Believed that any impression of change is illusory’Äîthat Reality is constant and eternal. See more in HW.

Democritus -460 ’Äî -352

With his teacher, Leucippus, postulated the existence of a mechanical, atomistic explanation for the world. Crucial and controversial: his introduction of the "void" or "vacuum" as an essential feature.

Plato -427 ’Äî -347

One of the most influential Greeks, influencing mathematics, educating Aristotle, and providing much of the formal dogma of the early Christian church.

Aristotle -384 ’Äî -322

The greatest influence on physics before Copernicus and Galileo.

Aristarchus -310 ’Äî -230

Mathematician and responsible for many calculations of distances...also an originator of a workable heliocentric model of the solar system.

http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Aristarchus.html

Claudius Ptolemy 87 ’Äî 150

The paradigm example of "saving appearances" is Ptolemy's epicycle model of the motions of the planets. It lasted in its original form for nearly 1500 years as described in his classic book. (He's also the first cast member to have a first and last name.)