Plato (circa 428 - 348 BC)
- Student of Socrates (c. 470 - 399 BC)
- Teacher of Aristotle and Euclid
- Emphasized metaphysics (logical principles) and the importance of the
circle and sphere in models.
- Believed that deductive reasoning was supreme.
- Believed sensory experience to be subjective, that pure thought was
preferable to experiment.
- Believed that Philosophy was the work of the mind and that manual Labor
was for slaves.
- Urged astronomers to think about the heavens, but not to waste
their time observing them.
- Believed that the Physical World is merely a shadow of the perfect world
of the forms.
Aristotle (384 BC – 322 BC)
- A student of
Plato and teacher of
Alexander the Great.
- Along with
Socrates
and Plato,
Aristotle was one of the most influential of
ancient Greek philosophers.
- Worked in almost every field of known "science" and philosophy.
- Believed that the Earth and the Heavens were governed by 2 different
sets of laws.
- Developed the geocentric (Earth-centered) model of the Universe.
- Reasoned that Earth was spherical based on observations of Earth's
shadow on the Moon, the fact that different stars can be seen farther south
than Greece, etc.
- Showed Moon is spherical.
- Believed that "natural" motion is straight lines on Earth, circles in
Heaven.
- Assumed an Earth centered Universe (everything falls to the center of
the Earth).
- Dominated cosmology for 1800 years.
Calling into question early, though persistent, Aristotelian thinking, Mark
Twain once exhorted:
"The Nature, which delights in periodic repetition in the heavens, is the same
nature which rules the affairs here on Earth. Let us not forget that lesson."
Return to class notes TOC.