Why Plato thought that medical drugs didn't work

They're worse than useless, he believed.

In the Timaeus, Plato lays out a sprawling account of the origins of the universe at the hands of caring and diligent gods, all the way down to the beginnings of human and animal life. If these gods are so diligent and caring, why didn’t they design bodies that don’t undergo sickness and death?

Well, it turns out: they couldn’t. Disease is just a necessary feature of the human experience.

The gods who designed our bodies are not all-perfect beings. Their heart is in the right place, no doubt, but their power is limited. But sickness and death are not entirely bad, anyway: the universe is home to a great variety of life, and this in large part is due to the fact that living things die and are replaced.

We humans can’t cure disease any more than the gods could make our bodies perfect, Plato thought. In an earlier post, I talked about Plato’s belief that we could prevent disease by exercising. That’s true: Plato’s preferred method for keeping a body healthy was keeping it in motion. That doesn’t mean that this is a perfect method, though: it worked well enough for Plato to recommend it, but he knew very well that nobody could stave off disease indefinitely.

Plus, it is purely preventative. What about the possibility of curing a disease after we have contracted it? Plato is emphatic: drugs don’t work.

Plato’s being quite controversial here. His contemporaries used drugs. No school of medical thinkers in antiquity ever exclusively relied on drugs. Many more preferred lifestyle changes, especially dietary modifications, but there was a growing interest in pharmacology, and it is precisely this that Plato in the Timaeus tried to counter.

One problem that he perceived, probably the smaller problem, was that drugs induce in us a kind of motion that just isn’t very good. In the earliest post on exercise, I focused on this line of thinking because, in contrast, Plato believed that the motions induced by exercise are the best kind of motion. When we exercise, we move ourselves. And self-motion is precisely the sort of motion that the whole universe is engaged in. To the extent that our bodies are like smaller versions of the universe, we should try to imitate this cosmic motion.

Here’s what Plato says: “now the best of the motions is one that occurs within oneself and is caused by oneself. This is the motion that bears the greatest kinship to understanding and to the motion of the universe. Motion that is caused by the agency of something else is less good. Worst of all is the motion that moves, part by part, a passive body in a state of rest, and does so by means of other things. That, then, is why the motion induced by physical exercise is the best of those that purify and restore the body” (Timaeus 89a).

So, what he means is that self-motion is the best kind of motion. The worst kind of motion, on the other hand, is motion that moves parts of our body indirectly while our body is at rest. That’s what drugs do.

That doesn’t mean that drugs are entirely useless, however. He is clear about this: this “type of motion is useful in an occasional instance of dire need; barring that, however, no man in his right mind should tolerate it. This is medical purging by means of drugs” (Timaeus 89b).

In other words, you might consider using drugs when your need is dire, but not otherwise.

You might be asking yourself: why not? If we are so sick that we are unable to move our bodies, why not engage in the worst kind of motion and take a drug?

That’s because there’s more to Plato’s view than simply a ranking of motions.

Plato believes that drugs run the risk of aggravating diseases.

Here’s what he says:

“We should avoid aggravating with drugs diseases that aren’t particularly dangerous. Every disease has a certain makeup that in a way resembles the natural makeup of living things. In fact, the constitution of such beings goes through an ordered series of stages throughout their life. This is true of the species as a whole, and also of its individual members, each of which is born with its allotted span of life, barring unavoidable accidents. […] Now diseases have a similar makeup, so that when you try to wipe them out with drugs before they have run their due course, the mild diseases are liable to get severe, and the occasional ones frequent. That is why you need to cater to all such diseases by taking care of yourself to the extent you are free and have the time to do that. What you should not do is aggravate a stubborn irritation with drugs” (Timaeus 89c-d).

This long passage contains the heart of Plato’s concern about drugs. Diseases are a lot like living things. Just as we go through stages of life, progressing naturally from childhood to adulthood, diseases also go through stages. Perhaps, for instance, the start of a disease features runny noses and then the end features fevers.

You can’t stop this progression. Drugs promise to be able to do that. Plato, of course, prefers exercise: prevent the disease from occurring in the first place with a healthy dose of prevention. But if you do get sick, you have to wait it out because even if the drugs is promised to lessen symptoms or end the disease a bit early, what is more likely to happen is much worse.

The drugs might aggravate the disease.

A disease that usually involves mild symptoms might now involve intense symptoms. A disease that tends to recur infrequently might now recur more frequently.

Again, that doesn’t mean that there isn’t an appropriate time and place to take a drug. We might imagine someone who is going to die from a disease. At that point, Plato might judge that the risk is worth it.

The important point is that we should never prioritize pharmacology — not even close, really. Pharmacological options have a huge risk attached to them, and, given the nature of disease and the inferiority of drug-induced motions, there isn’t much reason to suspect that they’ll work. Instead, we should rely more heavily on preventing disease in the first place.