Protagoras and the Marketplace of Ideas

John Stuart Mill’s famous celebration free speech is often pithily summarized as a defense of the “market place of ideas.” That characterization is not perfectly appropriate for the free-speech arguments set out in On Liberty, but it’s good enough. Mill isn’t quite as naïve about free speech as the metaphor might imply, but he’s still pretty naïve: 

Were an opinion a personal possession of no value except to the owner; if to be obstructed in the enjoyment of it were simply a private injury, it would make some difference whether the injury was inflicted only on a few persons or on many. But the peculiar evil of silencing the expression of an opinion is, that it is robbing the human race; posterity as well as the existing generation; those who dissent from the opinion, still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth: if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error.

It's not unreasonable to associate that argument with a crude account of market dynamics in which competition promotes the good (the true) and drives out the bad (the false). For what it’s worth, a much younger John Stuart Mill had far more sensible things to say about free speech:

I have not any great notion of the advantage of what the ‘free discussion’ men call the ‘collision of opinions,’ it being my creed that Truth is sown and germinates in the mind itself, and is not to be struck out suddenly like fire from a flint by knocking another hard body against it. (emphasis original)

While Mill himself never directly uses the metaphor, the "market place of ideas" is explicitly invoked by Plato in his Protagoras. (I like the Protagoras, I’ve blogged about it before).

Protagoras, the most famous of the sophists, has come to Athens to share his teachings. Hippocrates, a young Athenian, wants to learn from the famous master, and so he runs to Socrates so that they might go together. Hippocrates is keen on seeing these two wise men duke it out. (He gets his money's worth, so to speak). 

Socrates is taken aback by Hippocrates’ enthusiasm, and he warns the young gentleman against the dangerous effects that can come from exposure to sophistry. Sophists, according to Socrates, are “a kind of wholesaler or retailer of the wares by which a soul is reared.” In other words, they are salesmen of ideas. And because the ideas they sell relate to the state of one’s soul, they are salesmen of the most dangerous sort.

Socrates explores the market-for-ideas analogy:

And see to it, comrade, that the sophist, in praising what he has for sale, doesn’t deceive us as do those who sell the nourishment of the body, the wholesaler and the retailer. For they themselves too, I suppose, don’t know what among the wares they peddle is useful or worthless to the body—they praise everything they have for sale—and neither do those who buy from them, unless one happens to be an expert physical trainer or a physician. So too those who hawk learning from city to city, selling and retailing it to anyone who desires it any given moment: they praise all the things they sell. But perhaps some of these as well, the best one, are ignorant of what among the things they sell is useful or worthless to the soul. And so too are those who buy from them, unless one happens to be a physician expert in what pertains to the soul. (emphasis mine)

Socrates has pointed out something important. If the peddlers of ideas are like salesmen, then of course we should not trust them! Salesmen aim to sell. And so they will lie and deceive in order to make the sale. Worse than that, often the salesmen don’t even know the value of what’s on offer! They don’t care. Again, the goal is just to make the sale. There are potentially devastating information asymmetries in this market! A market of ideas is a failed market if ever there was one.

Only an expert can properly judge the quality of the products for sale. But this raises a problem. If the expert can already discern the good ideas from the bad, why would he need to buy the ideas in the first place? And if the buyers in the market lack the capacity to judge what it is they are buying, why should we expect the “good” ideas to out-compete the bad ones?

Socrates continues:

If, then, you happen to be a knower of what among these things is useful and worthless, it’s safe for you to buy learning from Protagoras and from anyone else whatever. But if not, blessed one, see that you do not roll the dice and run risks with the dearest things. For there is indeed much greater risk in the purchase of learning than there is in that of foods: it’s possible to buy food and drink from the retailer and wholesaler and to take them off in other containers; and it’s possible, before taking them into the body by drinking or eating them, to set them down at home and take counsel by calling upon someone knowledgeable as to what one should eat or drink and what one shouldn’t and how much and when. As a result, the risk involved in the purchase isn’t great. But it isn’t possible to carry off learning in another container. Instead, for one who has paid the tuition and taken the instruction into the soul itself through having learned it, he necessarily goes off having already been harmed or benefited thereby. (emphasis mine)

The marketplace metaphor trivializes ideas in a terribly misleading way. Ideas aren’t commodities. They are not the sorts of things we can try out and toss out when we tire of them. Once we are educated in a particular way, our soul has been shaped. There is no more competition, no more market pressure. We are done for, and so we better hope that the education we’ve received was a good one! That’s why exposing people (especially young people) to noxious ideas isn’t a harmless exercise of pedagogy, it is a dangerous act that can produce irreparable harm.

Quotations are from Stephanus pages 313-314 using the Robert Bartlett translation.