Plato’s mistake

Why it’s a bad idea to model one’s metaphysics on the rigor of mathematics

Plato’s Academy mosaic from the villa of T. Siminius Stephanus in Pompeii, Wikimedia.

What is your take on metaphysics? Mine is not particularly positive. At least, I am deeply suspicious, and largely reject, the whole approach to the field known as “analytic” metaphysics, which has been dominant since the beginning of the 20th century. (I am increasingly skeptical of the value of all analytic philosophy, but that’s a story for another time. And no, I’m no friend of the continental tradition either!)

My favorite whipping boy is a leading analytic metaphysician, David Chalmers, who initially became famous for his notions about consciousness and philosophical zombies, and has more recently embraced equally problematic notions like panpsychism. Chalmers and his colleagues proposed their “theories” on the basis of their intuitions and of what they find “conceivable,” regardless of whether there is any empirical evidence for their speculation. Indeed, they tend to be contemptuous of empirical evidence, dismissing it as the result of a “reductionist” approach to understanding things.

For instance, one of Chalmers’ most eminent colleagues, Philip Goff, claims that he has come up with a whole new way of doing science to correct what he calls “Galileo’s error.” He writes: “[Galileo] propose[d] a radically new philosophical theory of reality. According to this theory, the qualities aren’t really out there in the world, rather they’re in the consciousness of the observer. The redness of the tomato isn’t really on the surface of the tomato but is rather in the consciousness of the person perceiving it; the spiciness of the paprika isn’t really in the paprika but in the consciousness of the person consuming it. To return to the example we began with, when a tree comes crashing down in a forest, the crashing sound isn’t really in the forest, but in the consciousness of an onlooker. No onlooker, no consciousness, no sound.”

To begin with, this is not what Galileo proposed. Rather, he suggested that what we call secondary “qualities,” such as colors, sounds, smells, etc., are the result of the interaction between physical aspects of the world and our perceptive apparatus. For instance, “red” is not out there independently of an observer, but the wavelengths of light that—in animals such as human beings—trigger the sensation of red, are indeed out there. Similarly for the tree falling in the forest: no, it doesn’t make a sound—because sound requires a perceptive apparatus—but it does move air molecules regardless of whether anyone is around to perceive such movement.

Galileo strikes me as being exactly right, but Goff, and more recently Chalmers, are convinced that “qualities” are inherent in the world, because consciousness itself is a basic, elemental property of matter. The fact that professional physicists have dismissed the notion as nonsense on stilts doesn’t move these people one iota.

And that’s precisely the problem. Much (though not all!) modern metaphysics appears to be done in a vacuum that has effectively sealed itself off modern science and the empirical evidence that is the ultimate arbiter of scientific disputes. This isn’t exactly a new phenomenon in the history of philosophy. In fact, one could reasonably argue that the origins of modern science are rooted precisely in the rejection of the sort of metaphysics that Chalmers and Goff still indulge in, and which at the time was done by the likes of René Descartes.

Descartes thought of himself as a natural philosopher, just like Galileo (they were contemporaries). The reason we remember the latter as a scientist and the former as a philosopher is because Galileo was a better physicist and Descartes a more interesting philosopher. But physics detached itself from the sort of metaphysics precisely at the time of Galileo (and later Newton). It was followed by chemistry (with Boyle), then by biology (Darwin), and finally by psychology (James). In a sense, the sciences are the daughters spawned by philosophy, and analytic metaphysics is a last desperate (and doomed, in my opinion) attempt by the mother to keep her offspring in check.

Yet even even Descartes was not the originator of this style of doing metaphysics, but rather the last great philosopher to implement it. Arguably the real culprit is non other than Plato himself, much closer to the very beginnings of western philosophy. I’m not going as far as Alfred North Whitehead, who famously said that “All of Western philosophy is but a footnote to Plato,” but certainly a lot of western metaphysics is. And being a footnote ain’t no compliment.

Plato allegedly had this inscription at the entrance of his Academy: “Let no one ignorant of geometry enter.” Why? Because he had been deeply influenced by the Presocratic Pythagoras of Samos and his mathematical approach to philosophy. Plato reckoned—not at all unreasonably—that if he could establish the kind of philosophy he wanted to do on bases as rigorous as Pythagoras’ math and geometry then he would be getting somewhere.

That was the beginning of what is often referred to as the rationalist (as distinct, and often opposed to, the empiricist) approach to philosophizing that connects Plato, much Medieval philosophy, all the way to Descartes, and ultimately to Chalmers and Goff (and a number of others, to be fair).

Rationalism is the notion that the best way to figure things out about the world is by thinking about it. Really hard, and really rigorously. It is rooted fundamentally in logic, and it therefore bears a strong family resemblance with, you guessed it!, mathematics. With one important difference, which turned out fatal for the rationalist program in philosophy: mathematics, like logic, is independent of the real world. It is a non-empirical system within which you can prove or disprove all sorts of interesting things because they are, or they are not, entailed by whatever set of premises or axioms you choose. Sure, logic and math turn out to be useful in the real world as well (because the real world is made of a subset of logically-mathematically consistent objects), but they are fundamentally independent. Logicians and mathematicians don’t need to go around testing their theorems empirically. Scientists have to.

What about metaphysics? It is supposed to tell us something about how the world actually is, not how infinitely many possible worlds might have been. And figuring out how the real world is simply can’t be done without a heavy input of empirical evidence—as David Hume was one of the first to forcefully argue, in his case in reaction to the excesses of Medieval Scholastic philosophy. That is why science detached itself from the Plato-Cartesian mode of doing things and started messing around with facts and data. And I don’t have to tell you which approach—science or Chalmers-style metaphysics—has been more successful over the past four centuries or so.

Plato’s mistake was understandable, by the standards of the time. Not only he was duly impressed by the successes of the mathematicians, he was also reacting against the rather unfounded speculations about the nature of the world put forth by the so-called Presocratics.

One such Presocratic was Anaxagoras, who lived from 500 BCE to  428 BCE. He proposed a number of ideas about the world: that it is governed by a Cosmic Mind (Nous), that life exists throughout the cosmos, and that the Sun is actually a fiery mass “larger than the Peloponnesus.” He was right about the Sun, wrong about the Cosmic Mind, and the jury is still out there as far as extraterrestrial life is concerned.

But the point is not that Anaxagoras—or any of the other Presocratics—happened to be right or wrong about specific notions. The point is: how did they know? What sort of evidence did they have for their claims? Or, to put it in modern philosophical terms, how close to each other were their metaphysics and epistemology?

Socrates, Plato tells us in the Phaedo, once read a book written by Anaxagoras, and was initially very excited at the prospect of figuring out how the world works. But he was soon disappointed:

“What expectations I had formed, and how grievously was I disappointed! As I proceeded, I found my philosopher [i.e., Anaxagoras] altogether forsaking mind or any other principle of order, but having recourse to air, and ether, and water, and other eccentricities. I might compare him to a person who began by maintaining generally that mind is the cause of the actions of Socrates, but who, when he endeavored to explain the causes of my several actions in detail, went on to show that I sit here because my body is made up of bones and muscles; and the bones, as he would say, are hard and have joints which divide them, and the muscles are elastic, and they cover the bones, which have also a covering or environment of flesh and skin which contains them; and as the bones are lifted at their joints by the contraction or relaxation of the muscles, I am able to bend my limbs, and this is why I am sitting here in a curved posture—that is what he would say, and he would have a similar explanation of my talking to you, which he would attribute to sound, and air, and hearing, and he would assign ten thousand other causes of the same sort, forgetting to mention the true cause, which is, that the Athenians have thought fit to condemn me, and accordingly I have thought it better and more right to remain here and undergo my sentence.” (2.6)

This is a fascinating passage because Socrates is criticizing Anaxagoras for being, as we would say today, a reductionist. Anaxagoras “explains” Socrates’s current situation in terms of physical attributes, neglecting to mention the most relevant cause of them all: that the Athenians have sentenced him to death. But Anaxagoras and the Presocratics could also be criticized for attempting to arrive at explanations about the world by sheer force of thinking, without empirical evidence. As a result, sometimes they got it right (but how would one know?), and most times spectacularly wrong.

Don’t misunderstand me: the Presocratics represented a monumental step forward in human understanding, as they abandoned the “poetic” explanations of the world put forth by the likes of Hesiod and Homer and replaces them with explanations in terms of natural causes. They truly were proto-scientists. But it wasn’t until Aristotle that science actually got going. He bothered to get his hands dirty and actually carry out empirical observations on the basis of which he established, among other things, his biology.

The parallel traditions of rationalism and empiricism then co-existed from Plato and Aristotle on until Kant (after he was awakened from his “dogmatic slumber” by Hume) eventually merged them. It then became clear that theoretical reasoning by itself isn’t going to provide us with knowledge of Nature. And neither are theory-independent observations. We need both theory and empirical data to go hand-in-hand. And this is how, as I said, modern science got started beginning with Galileo.

Unfortunately, analytic metaphysics took a giant step backwards, renewing and perpetrating Plato’s mistake. Which is why the question about Chalmers, Goff, & co. isn’t whether they are right or wrong. They may or may not be, there is no way to tell. As the physicist Wolfgang Pauli said (with regard to a scientific paper that he thought was really, really bad), these people are “not even wrong.”

Is there a better way to do metaphysics? Yes! It’s what is sometimes referred to as naturalistic, or scientific metaphysics, and has been championed by a number of contemporary philosophers, including James Ladyman and Don Ross. They suggest that the proper role of metaphysics isn’t unbridled speculation a la Presocratics-to-Chalmers, but rather the crafting of a comprehensive worldview based on the best findings of science.

Individual sciences, and individual scientists, can’t do that because they’re busy with running experiments and writing the grant proposals that fund them (trust me, been there, done that). But metaphysicians can step back and take a look at the bigger picture, comparing, contrasting, and integrating the findings of individual sciences. In a sense, this makes metaphysics a branch of philosophy of science, which—as a philosopher of science myself—I certainly welcome.

So let us recognize Plato’s mistake for what it was: the mirage of certain knowledge of the world modeled on the advances of mathematics and logic. Let us then cast aside that kind of metaphysics and instead get down to the lab to see what the scientists are up to.