Traditionally, much economic theory assumes that humans are perfectly rational economic actors – we do things that are in our economic self-interest and avoid things that aren’t.  More recently, economists have increasingly come to recognize that actual people aren’t always as predictable as the models predict.  Despite the growth of behavioral economics (which does try to account for economics in light of real human behavior and psychology), in my limited understanding the assumption of “homo economicus” remains fundamental to most economic theory, especially the so-called “Chicago School.”

I would never have thought to look for homo economicus in the Talmud, but he popped out at me the other day.  The Babylonian Talmud (Avodah Zarah 34b) discusses the permissibility of fish sauce produced by non-Jews, whether for consumption or deriving benefit (e.g., engaging in commerce in it).  Fish sauce, made primarily from fermented, oily fish like anchovies was an important and popular condiment in antiquity (and continues to exist in the form of Worcestershire sauce).  The rabbis had two potential worries: (1) that unkosher fish would be used; and (2) that gentile wine would be mixed in.  It is the concept of homo economicus that is brought to solve both problems:

(1)  A skilled maker of fish sauce can be assumed to be using only one kind of (kosher) fish, because mixing in other kinds of fish would degrade the product and thus lead him to lose business;

(2)  Wine really isn’t that good in fish sauce, so it would only be added in order to dilute it so one could sell more.  But in the places that make fish sauce wine is more expensive than the sauce!  So it would make no sense to add wine, and thus the sauce need not be supervised and is permitted.

Both of these answers assume that non-Jews are rational economic actors; they don’t, for example, just want to add wine because of one person’s idiosyncratic tastes or out of maliciousness.  This is somewhat surprising, as rabbinic literature contains all kinds of assumptions about gentiles that do not always have them act “rationally.”

More interesting to me, though, is the economic assumption embedded in this discussion.  The stakes here, from a rabbinic perspective, are surprisingly high: to benefit from a substance used in idolatrous worship (i.e., the wine from which a libation was made) is akin to idolatry, seen as a grievous sin.  Yet the assumption of rational economic action is so strong that it outweighs the possibility that such wine was used in the fish sauce.  I am sure that this assumption appears elsewhere in rabbinic literature, and it would be interesting to see where and how consistently.

Now, if I was only as rational actor as both the University of Chicago and the Talmud say I should be….