Ancient Greece is the place and time where the people of what was to become our Western Civilization first engaged in lengthy, thought-out, rational discourse on nature, morals, society, and everything else they’ve encountered. This became known as philosophy, and the works of the greek philosophers became the foundation of the philosophy of the modern world, producing also logic, mathematics, political and social sciences, and greatly influencing science. The influence of the ancient greeks is so great, A. N. Whitehead said in his often-quoted 1979 work “Process and Reality” that the safest general characterization of the European philosophical tradition is that it consists of a series of footnotes to Plato.
There’s no sensible way for me to describe all of it in one small web page, all I can is to point at the three major figures and some of their influences on the modern world. Little is known of the early development of the ancient greek thought, but starting with the Seven Sages of 6th century BCE, the history becomes documented, we know about the different, sometimes conflicting, schools of thought – Milesian, Pythagorean, Eleatic, Pluralistic, Atomistic, Sophistic, spanning three centuries of the development of natural philosophy, cosmology, mathematics, epistemology, logic, ethics and aesthetics, but today all of these schools are simply known as “pre-Socratic”, because in the eyes of the generations to come, they were eclipsed by Socrates, Plato, and Aristotle.
Socrates is, of course, the sophist who became famous for developing critical thinking by means of Socratic questioning, a method of systematic questioning to uncover assumptions, explore the consequences, and otherwise analyze every philosophical statement. The central technique of this method, Elenkhos, was a chain of logical questions intended to bring any given generic statement to aporia, the state of self-contradiction, thus forcing the refinement or abandonment of the premise, with no actual directives given by the questioner. This proved to be so effective at exposing the declining Athenian ethics, that he was sentenced to death for “corruption of the minds of the youth of Athens”.
Then, of course, we had Plato (a student of Socrates) with his Theory of Forms, the belief that the physical world consists of nothing but false shadows of the Forms, the shadows that change and perish, while the world of ideas is the higher, true, and the most fundamental reality, and that the true knowledge cannot come from observation but rather from insight and critical reasoning. Plato’s most famous student, Aristotle, took the opposing view, grounding his knowledge in the observable, objective reality, and stating that there are no a priori forms, that the Universals are, instead, instantiated in the Particulars and cannot exist without them. He explored logic and deductive reasoning in 4th century BCE to such detail that only the mathematical logic of the 19th century managed to advance further. Believing thus that the study of nature is useful, he studied it as rigorously as was possible at the time, hindered by the lack of quantitative concepts and measures, he still managed to contribute greately to what was to become botany, zoology, physics, astronomy, and chemistry.
To me, the contrast of Plato and Aristotle is the first example of the eternal conflict in natural philosophy, the conflict of deduction and induction, a priori and a posteriori, nature and nurture, internalism and externalism, rationalism and empiricism, and, most recently, critical rationalism and scientific realism.