At first glance, the philosophers of the Ionian school may not overly impress you. Thales—Western history’s first recorded philosopher—thought that everything was made of water; Anaximenes, belonging to the same school, thought it was air; and Herlaclitus, selecting among the remaining elements, thought it was fire. Anaximader, probably the most sophisticated of the bunch, thought it was some boundless, eternal substance called apeiron. None of them conducted any controlled experiments. 

Considering what we now know about the atomic theory of matter, these hypotheses all come across as very crude—and of seemingly little contemporary value. If I want to learn about the natural world, and I know, for example, that water is composed of hydrogen and oxygen—containing only 2 out of 118 known elements—then I’d be better off reading a good book about chemistry or physics than wasting my time on Thales. Thinking that everything is made of water, or air, or fire is not going to get me very far. 

But we should really be more charitable. Consider that, at the time, the next best explanation for natural phenomena, things like thunder, was that it was the result of Zeus hurling down lightning bolts in anger from above; or that the Sun was really the god Helios driving his chariot across the sky each day; or that earthquakes were (obviously) the result of Poseidon striking the ground with his trident. 

Against this background, the Ioanians were the first to cast aside this infantilizing mythology in the search for fully materialist causes of natural events—and this alone should be rightfully celebrated. 

But the Ionians, and in particular, Thales, gave us something much grander than this. They gave us the intellectual tools that would drive all subsequent progress in knowledge—methods of thinking that would ultimately lead to the establishment of modern science, and with it, the rejection of supernaturalism in all its inglorious forms. 

Thales’s invention of critical rationalism

It takes a reflective mind to propose that, despite all the apparent variety in the world, everything, at bottom, is made of some unitary, fundamental substance. As far as we know, Thales was the first to do this, and introduced the idea that there is a difference between appearance and reality—that our senses can deceive us—and that the investigation of the world should be predicated on the idea that reality is often hidden from our common sense notions of how things seem. 

In addition to proposing that all is made of water, Thales also believed that the earth rests, or floats, on water. If the earth, as it was believed, was stationary and central to the universe, then an explanation was needed as to what supported the earth in this preeminent position. Thales, fittingly, thought the earth floated on a cosmic ocean like a piece of wood floats in the sea. 

What happened next is nothing short of extraordinary—the greatest gift the presocratics gave us. It will take a bit of explaining to convey its importance. 

Anaximander, Thales pupil, and part of the same Ionian school, proposed a radically different hypothesis concerning the position of the earth. The earth, according to Anaximander, floats freely in the center of the universe.

According to the philosopher of science Karl Popper, Anaximander likely arrived at this conclusion by criticizing Thales’ assertion that the earth rests on water. Anaximander noted that, if the earth is supported by water, we would then need to know what supported the water itself, and then what supported that, ad infinitum. Anaximander therefore hit upon the problem of infinite regress (the same problem creationists encounter when asked, if God created everything because everything requires a cause, then what created God?) To prevent this regress, Anaximander proposed that the fundamental substance of the universe is eternal and boundless and that, if the earth is at the center of this space, it has nowhere to go, nowhere to fall, nowhere to be pushed. 

This is quite remarkable in itself, and would ultimately lead to further cosmological theories that allowed for the movement and position of astronomical bodies around the circumference of the earth. But what it more importantly signifies—from an epistemological perspective—is that the path towards progress in our understanding of nature lies in the free criticism of ideas—even, and especially, among adherents of the same school. 

It’s disheartening to realize how uncommon this was throughout much of human history and even among the Greeks. The Pythagoreans, for example, as well as the later schools of Plato and Aristotle, and of course the monotheistic religions, mostly considered the founder of their respective traditions to be, in some sense, infallible and beyond question. This is why Aristotle held back the progress of science for so long, and why organized religions are mostly regressive and reactive.

If you’re a Christian, for instance, you had better not criticize, reject, or otherwise alter any of the teachings of Jesus (or whatever happens to be considered orthodoxy in your community), else you cease to be a Christian. Go against this orthodoxy, and you face the charges of heresy or blasphemy—punishable by expulsion from the community or, in some cases, death. In other words, criticism is not tolerated; the study and promulgation of already existing, infallible, permanent knowledge is all that is required—and expected—in closed systems of thought. Dogma is the name of the game. 

Even Plato would later complain that Aristotle, in criticizing his theory of Forms, “spurns me, as colts kick out at the mother who bore them.” You simply were not expected to challenge your masters. And if you did, they made their displeasure widely known. 

But look what happened with Anaximander. Not only did he criticize Thales, he flat-out rejected him. He proposed an entirely different theory on the grounds that, due to the problem of infinite regress, Thales’s account wasn’t even coherent. And yet, there seems to be no indication that Thales was ever upset about any of this! Anaximander was not labeled a heretic and expelled from the school, forced to establish his own. He remained a part of the Ionian school doing what Thales must have encouraged—thinking critically about the nature of the world, wherever that led. 

As Popper wrote:

If we look for the first signs of this new critical attitude, this new freedom of thought, we are led back 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. (They seem to have died within a few years of each other.) 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 Popper thought 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.” Popper has to be right here; students trained in a dogmatic school would hardly be so keen to openly contradict their master in such a thoroughly destructive way. It would be like a follower of Jesus advancing the idea that Jesus had no divine relationship to God whatsoever, but was just a wise human teacher, and the Church being totally fine with it. That this idea seems so laughably improbable to us proves the point, and convinces us that Thales had to have actively encouraged the critical spirit. 

Unlocking the secret to intellectual progress

According to Popper, there is only one “true theory of knowledge,” “the theory that knowledge proceeds by way of conjectures and refutations.” Popper advanced the notion that when asked, personally, how you can know something, the proper response is, “I don’t; I only propose a guess. If you are interested in my problem, I shall be most happy if you criticize my guess, and if you offer counter-proposals, I in turn will try to criticize them.” All knowledge is therefore provisional and subject to revision through open dialogue and critical discussion. It’s the reason we no longer believe earthquakes are caused by Poseidon’s trident.  

This happens to be the perfect encapsulation of the epistemological approach of the Ionian school—where every new generation of thinkers disagreed with each other—and also of the institution of science—humanity’s greatest invention. What is remarkable is that this approach was developed over 2,600 years ago, at the very birth of natural philosophy, by Thales—the initiator of this noble tradition. 

We would all be wise to heed Thales’ example: namely, to remain open and curious, to encourage criticism of even our most cherished ideas, and to commit allegiance to nothing other than the truth. It’s hard to see how such an infusion of intellectual humility is not exactly what the world needs right now. 

References

• Karl Popper. Conjectures and Refutations, the Growth of Scientific Knowledge.
• G. S. Kirk. The Presocratic Philosophers: A Critical History with a Selection of Texts.
• Thales of Miletus. Internet Encyclopedia of Philosophy. 
• Anaximander. Internet Encyclopedia of Philosophy. 
• Karl Popper: Critical Rationalism. Internet Encyclopedia of Philosophy. 

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