In the comments on my post, Leiter contended that I simply did not understand the distinction between synchronic and diachronic. He invoked the work of philosopher David Velleman for the proposition that this is not simply an empirical but also a "conceptual" distinction. So I went to Velleman and found that Leiter was right. I had mistakenly inferred that Leiter and Velleman had been making points about actual animals (and thus actual vegans), rather than the concept of animals (and thus the concept of vegans). For Velleman and Leiter, "conceptual," it turns out, means "imaginary." In getting his argument about the difference between humans and non-human animals going, Velleman says (at page 81 of The Possibility of Practical Reason) the following: "Consider a nonhuman animal, such as a cow or a pig. I assume that a cow cannot perceive of itself as a persisting individual and consequently cannot conceive of itself as enjoying different benefits at different moments in its life." The assumption is apparently constitutive of non-human animals for Velleman (and thus for Leiter).
Having been properly informed, I am now ready to concede: 1) Imaginary cows, pigs, and other non-human animals cannot conceive of themselves as persisting individuals; and 2) On the imaginary farms where the imaginary cows, pigs, and other non-human animals are treated humanely their whole lives and then unexpectedly and painlessly zapped by a death ray, the imaginary animals do not experience any harm other than the deprivation of future pleasure (which, Velleman says, those particular animals can't experience anyway, because they cannot persist as beings).
No doubt I have missed some important subtlety here, but even if so, I think this little exercise illustrates a larger point that a number of other commentators made on my earlier post: Philosophy as a discipline limits its relevance when it bases arguments on counter-factual assumptions. Philosophy is hardly unique in this respect, however.
Consider economics. If pressed, most economists will concede that the assumption of rational actors is not intended to model human behavior perfectly, but will say that the rational actor assumption makes pretty good predictions in general and very good predictions in some contexts. But even though most economists understand the counter-factual nature of the rationality assumption at some level, they often forget it when talking about real-world issues. For example, in a recent Planet Money podcast, U Chicago B School Professor (and economist) Emily Oster engaged in the following colloquy (which I am paraphrasing for simplicity rather than quoting in full):
Q: Why are restaurant meals bigger than they used to be?
Oster: Because food got cheaper.
Q: But why didn't restaurants keep portion sizes constant and lower prices?
Oster: Because people really like to eat.
Q: But isn't all that extra eating costly because obesity is unhealthy?
Oster: Not nearly as costly as it used to be, now that people have desk jobs that don't require them to move very much and we have medical treatments that extend the lives of obese people.
Oster's first two answers make sense but the last one is an example of the phenomenon under discussion: She forgot to state (and perhaps simply forgot) the limits of the rationality assumption. Undoubtedly, there are some people who somewhat discount the cost of an unhealthy diet because they're banking on statins, liposuction and bypass surgery. But a truly rational actor would surely know that a healthy diet will lead to much better overall health than these measures--and indeed, millions of people in fact make that calculation: They consciously try to limit their intake of unhealthy foods but are unable to control themselves (because human beings developed the tastes we have under conditions of scarcity in which occasional binge eating was helpful). The feeling of having one's super-ego (urging restraint) at war with the id's appetite is so familiar, that only someone too enamored of her model could so grossly mischaracterize the fattening of Americans as simply a rational act.
Having trashed the myopia of philosophy and economics, I should add that I live in a glass house. We in the legal academy who spend some portion of our time analyzing judicial decisions know from political science and simple observation that legal reasoning as such does not account for all of what's going on in contested cases, and that in the most highly watched Supreme Court cases---about abortion, affirmative action, gay rights, gun rights, school prayer, and other hot-button issues--ideology no doubt accounts for the lion's share of results. Sometimes we make this point, at least as a caveat, but at other times we write as though judges would reach correct results simply by reading our brilliant articles, regardless of their particular ideological predilections.
My point is not that philosophers, economists, and legal academics should always couch every sentence in their academic work with a caveat about the assumptions being made. Within disciplines, it is surely an acceptable shorthand simply to make the assumption. However, when speaking to a wider audience, the disclaimers need to be made: Leiter is talking about hypothetical animals; Oster is talking about hypothetical obesity; and we legal academics (myself included) are talking about hypothetical judges. Such hypotheticals can have relevance for the real world, but only to the extent that the models work. Leaving out that caveat can be quite misleading.
Posted by Mike Dorf