Thales of Miletus, a presocratic philosopher born in 626 BCE, proposed that the underlying, fundamental substance of all matter was water, while his student Anaximander thought the substance was an indefinite material called Apeiron. Anaximenes, Anaximander’s student, disagreed with both and thought the fundamental substance was air, while Heraclitus disagreed with everyone and thought the substance was fire.
This is not, on the surface, a particularly impressive list of accomplishments for a group of philosophers. But, as has been pointed out many times, what is impressive is that each philosopher had their own elaborate naturalistic arguments in favor of their preferred explanation, in an age where beliefs were dominated by supernatural interpretations.
But there is another, even more profound lesson hidden in the irrelevancy of their cosmological theories, which was first explained by Karl Popper in his essay titled The Beginnings of Rationalism. Popper noticed the surprising fact that all of the above philosophers disagreed with each other despite coming from the same school.
Disagreements coming from different schools of thought are obvious and expected. We expect, for example, the Sophists to disagree with the Platonists and the Christians to disagree with the Muslims. The natural course of affairs is for people to identify with a group that defines itself in contrast to other groups, and then to defend the integrity of their chosen group against the doctrines of other groups. This is the well-known phenomenon of tribalism that plagues the human race.
What is exceptional about the Ionian school of philosophy is that the students actively and vigorously disagreed with their teachers and with the founder of the school, and, what’s more, that this must have been encouraged by the school’s founder, Thales. As Popper wrote:
“If we look for the first signs of this new critical attitude, this new freedom of thought, we are led to Anaximander’s criticism of Thales. Here is a most striking fact: Anaximander criticizes his master and kinsman, one of the Seven Sages, the founder of the Ionian school. He was, according to tradition, only about fourteen years younger than Thales, and he must have developed his criticism and his new ideas while his master was alive. But there is no trace in the sources of a story of dissent, of any quarrel, or of any schism.”
“This suggests, I think, that it was Thales who founded the new tradition of freedom—based upon a new relation between master and pupil—and who thus created a new type of school, utterly different from the Pythagorean school. He seems to have been able to tolerate criticism. And what is more, he seems to have created the tradition that one ought to tolerate criticism…Yet I like to think that he did even more than this. I can hardly imagine a relationship between master and pupil in which the master merely tolerates criticism without actively encouraging it.”
This is the key difference between ancient Greek philosophy (with the exception of the Pythagorean school) and any other dogmatic tradition, religious or philosophical. For instance, imagine how a member of the Catholic Church would be received if they questioned the divinity of Jesus, or how a dissenter would have been handled in Communist Russia.
In most traditions and cultures, schools and masters go unchallenged, and the goal is to keep the ideas of the founder alive and unaltered. In this situation, there can be no progress, and in fact no possibility of progress, as dissenters are labeled heretics and excommunicated from the group.
What the presocratics did was to discover the best tool humanity has for making progress, namely critical rationalism. Critical rationalism is founded on the concept that no knowledge is final, and that the more we learn, the more problems and questions arise. The best we can do is to say, “this is my theory, my best logical and coherent explanation of how the world works based on the evidence. But it is not final; if you disagree with it, do your best to criticize my theory and replace it with something better.” This is the spirit of progress and intellectual humility, and maps on perfectly to the history of knowledge and the major revolutions of thought that have occured in human history and the history of science.
The danger is, and has always been, believing that an idea or thinker is beyond refutation. As Popper points out, this happened first with Aristotle—who held back science for hundreds of years—and then with Newton, whose theories were shown to be inadequate by Albert Einstein.
No theory is final; knowledge can only represent the best current explanation to be provisionally accepted. And it is only via a process of free and uninhibited criticism that old theories can be shown to be inadequate and better theories can take their place.
Compare this mentality to our current state of political polarization, or to our tendency to search for an infallible guru to tell us what to do and what to think. While we are busy worrying about our identification with some group, we forget to criticize our own theories or our own group. For example, if we disagree with our in-group, or refuse to adopt every belief of that group, we’re labeled as an outsider without consideration to the merits of the argument. In this sense, it’s more important to conform than to think. (And if you find someone who you admire, and also find that you agree with everything they say, you’re probably not thinking hard enough.)
I’ve seen this happen, for example, with Steven Pinker. By any measure, Pinker is left-leaning politically and part of the liberal tradition. But because he is not far enough left, or does not conform to the mold of radical liberalism, his arguments are (by some) ignored and he’s ceded over to the conservative party, which is absurd.
Political labeling has come to replace argumentation and fact, and until we can get back to the spirit of critical rationalism, where we criticize our own group’s theories as intensely as other groups, we will remain stagnant and unable to solve social problems. Do we want to be part of a tradition that exists solely to transmit ideas unaltered, or do we want to exercise our critical faculties to the fullest extent to bring about progress and change?
Our primary concern should not be, “does my belief fit in with a particular ideological camp,” but rather, “does my belief fit in with the evidence and is it logically coherent.” Having intellectual integrity means valuing truth and consistency above all else.
This idea of intellectual humility is critical, and was once again thought of first by the presocratics. As Xenophanes wrote:
“The gods did not reveal, from the beginning,
All things to us, but in the course of time
Through seeking we may learn and know things better.
But as for certain truth, no man has known it,
Nor shall he know it, neither of the gods
Nor yet of all the things of which I speak.
For even if by chance he were to utter
The final truth, he would himself not know it:
For all is but a woven web of guesses”
For a concise overview of Karl Popper’s ideas on critical rationalism, check out Philosophy and the Real World: An Introduction to Karl Popper by Bryan Magee.
For a selection of Karl Popper’s best non-technical writings, including the essay The Beginnings of Rationalism, read Popper Selections, and for two modern interpretations of Popper’s ideas, read Critical Rationalism: A Restatement and Defence by David Miller and The Beginning of Infinity: Explanations That Transform the World by David Deutsch.
For more information on the presocratic philosophers, read The Presocratic Philosophers: A Critical History with a Selection of Texts by G.S. Kirk, or, for something a little less in-depth, read Presocratic Philosophy: A Very Short Introduction by Catherine Osborne.