Thompson notes, is that logic is supposed to deal with the form of thought, while life seems to belong only to its content: “how can anyone pretend that thought about living things differs in any such [formal] respect from, say, thought about planets?”33 (Similar incredulity that there should be anything formally distinctive about action may drive some of the opposition to praxeological apriorism.) But if Thompson is right, the logical form of natural-historical judgments (or, for praxeologists, of means-end explanations) is as irreducible as any other. Just as the criterion for something’s being an action is no list of physical features, but rather the applicability of praxeological categories and forms of description, so the criterion for something’s being alive is likewise no list of physical features, but rather the applicability of vital categories and forms of description, and in particular the applicability of natural-historical judgments; and our ability to apply such judgments reliably is rather like a biological equivalent of verstehen. (It’s also worth noting, though, that just as for Mises the applicability of praxeological categories to reality is guaranteed by the pragmatic incoherence of denying that one is acting, such denial itself being an action, so the applicability of biological categories to reality would seem to be guaranteed by the similar incoherence of denying that one is alive, such a denial being an action and therefore a vital operation.)
In biology as in economics, then, teleological categories are a priori; in addition to the logic of action we have a logic of life. (This is of course not to say that, e.g., it is true a priori that the heart is for the sake of pumping blood, any more than that it is true a priori that my trip to the store was for the sake of purchasing butter; what is a priori is not the content of such explanations but their form.) To say what a bodily part is for is to locate it in the context of what is normal for the species (in this irreducible, non-statistical sense of normality). Likewise, what counts as a good instance of some biological category (healthy leg, healthy digestion, healthy dog) is also determined by species normality. Just as, for Wittgenstein, nothing counts as speech absent the relevant context of
33 Thompson, op. cit., pp. 25-26.
R. T. Long – Wittgenstein, Praxeology, and Frege’s Three Realms – p. 23