Today Mandeville's Fable of the Bees (a book that evolved over many editions), is less read than it should be by Hume, Rousseau, Smith, and Kant scholars. It is completely forgotten by everybody else. There is, of course, a general sense that Mandeville defended the so-called (Hobbesian) 'selfish hypothesis,' but there is little detailed treatment of his brilliant moral psychology or his complex social theory in the literature (although Michael Gill's The British Moralists on Human Nature is a honorable, albeit partial exception). Libertarian students kind of know Mandeville via Hayek's high praise of Mandeville's treatment of unintended, spontaneous orders of all kinds of social institutions. Given that praise by Hayek dooms a reputation in some quarters, it is worth mentioning that Keynes happily recites and endorses part of the Fable at length in his General Theory.
Now earlier at NewAPPS, I already discussed Mandeville's critical attitude toward the high social status of mathematics in medicine (an argument that he anticipates in the Fable). Here I want to discuss a related criticism:
"Mr. Hutcheson, who wrote the Inquiry into the Original of our Ideas of Beauty and Virtue, seems to be very expert at weighing and measuring the Quantities of Affection, Benevolence, &c. I wish that curious Metaphysician would give himself the Trouble, at his Leisure, to weigh two things separately: First, the real Love Men have for their Country, abstracted from Selfishness. Secondly, the Ambition they have, of being thought to act from that Love, tho’ they feel none. I wish, I say, that this ingenious Gentleman would once weigh these two asunder; and afterwards, having taken in impartially all he could find of either, in this or any other Nation, shew us in his demonstrative way, what Proportion the Quantities bore to each other."--Mandeville, The Fable of the Bees or Private Vices, Publick Benefits, sixth dialogue between Horatio and Cleomenes (vol 2).
A problem in a quantitative science of human nature is to measure directly or by proxy some of the hidden mental qualities that we are most interested in (theoretically or politically). Let's leave aside the question how fair Mandeville is to Hutcheson, who is really after vindicating the idea that anybody that lives up to everyday responsibility can be a moral hero, Mandeville here calls attention to at least four distinct problems:
- The way we reveal our motives may not track our genuine motives; we have a lot of incentives to disguise our real motives, after all.
- Even allowing that outsiders or the persons concerned have access to motives, it is very difficult to disentangle different motives to action.
- Even if we can disentangle motives to action, it is very difficult to weigh motives quantitatively.
- Experts are not entirely unbiased spectators when they try to operationalize answers to 1-3.
Mandeville's reservations about the use of mathematics in medicine (recall here) and moral theory continue to be relevant to contemporary philosophy of social science. (By the way, Mandeville is the first to grant that in pure theory we should use mathematics liberally, and he also believes that mathematics can function as a very useful, inferential device.)
Following Samuelson, economists tackled the first problem by appealing to a doctrine of revealed preference (see also here). While this has been extremely influential, the problem has always been that it makes non-trivial bets about the psychological structure of homo economicus. In the secondary literature, the stability (Samuelson's first postulate) and transitivity (Samuelson's third postulate) of our preferences have been most scrutinized. Samuelson also insists that the units in which prices are stated is irrelevant (the second postulate), and this, too, is open to empirical challenge. Mandeville's moral psychology puts pressure on all three postulates (about which more some other time). Along the way, Samuelson also assumes that consumers are price-takers (and this is not the case in some markets). Now methodologically Samuelson's program can be defended, but there is no doubt that there is a huge risk in such stipulative bets on the nature of reality, which can lead a whole discipline down a garden path.
On the second problem, we have made genuine experimental progress during the last half century. Social psychologists and experimental economists are extremely skilled at creating ever-more-fine-grained experiments at disentangling different motives for given choice conditions. However, is unclear under what conditions we are permitted to apply the results from extremely constrained environments (the experimental set-up) to the world of social policy.
On the third, we have made no progress, and arguably it eventually led to the demise of psychological hedonism in utilitarianism. Even today the problem of weighing psychological qualities is often assumed away in many mathematical formulations of decision theory (but, of course, not by readers of NewAPPS).
On the fourth, there is now a thriving literature on expert bias and overconfidence. Of course, in practice the problem is nearly always limited to other experts.