There are two broad ways to conceive of the metaphysics of teleology. Teleology may be dispositional or it may be axiological. What distinguishes these two kinds of teleology is the source of the teleological relation. If teleology is dispositional, some item i has some end e in virtue of some metaphysical or explanatory relationship between i and e. This is the kind of teleology that philosophers of science such as Hempel, Braithwaite, Wiener, and Wright had in mind.[i] If teleology is axiological, on the other hand, i has e in virtue of some value that e instantiates. Axiological teleology is far more common in the literature, stretching through history from the Ancients to contemporary metaethics, epistemology, et cetera.
For e to be immanent in i, e must be in some way contained in or determined solely by i. That is, i must be autotelic. This means different things for dispositional teleology than it does for axiological teleology, however. Let’s begin with the former. If i has some immanent disposition to realise e, two conditions must obtain: (1) there must be something about i that reliably picks out e, and (2) e explains i. If only (1) obtains, there is no teleology. It is at best efficient or formal causation. For any instance of immanent teleology, e makes i reliably pick out e. While this may sound crazy, there is no shortage of accounts that attempt to make this intelligible. The most common is Wright’s account of teleology as causation by consequence, or what he calls consequence etiology. Wright’s (explanatory) schema is as follows:
i is an element of some system s for the sake of e if and only if both s is disposed to satisfy e in virtue of i given some normal condition c and s was disposed to satisfy e in virtue of i given c in the past.
Both (1) and (2) above have representatives in Wright’s schema. (2) here is self-consciously framed in terms of evolutionary adaptation. This need not be strictly biological, but biological evolution is the core of the account. Insofar as this is the case, however, there is a clear bait and switch. e here is not the end of i (ei) but the end of s (es). ei is not properly explanatory in any adaptation; i may be disposed to realise ei, but ei alone gives no reason for why i should be an element of s. For instance, it might be nice for spiders to have wings so they can fly. But they have no need for flight given the niche they occupy. The ability to fly is not sufficient for explanation. Rather, ei must contribute to es and hence the latter bears the explanatory and metaphysical significance. And this means that i is not autotelic. Rather, e is transcendent of i.[ii] The same pattern occurs for every known account of immanent dispositional teleology and seems to follow immediately from (2).
Axiological immanent teleology faces the same fate, though in a much more interesting way. If e is immanent in i then three conditions must be met: (3) e is valuable with respect to i, (4) i has some duty to obtain the value that e provides because e is valuable for i, and (5) e explains i. (5) here is of course familiar to us as the problematic condition in dispositional teleology, and one might think that it would be problematic here too. But this is not necessarily the case. It is common in the history of philosophy to suggest that existence is more valuable than non-existence. If this is the case, then the value that e provides might be sufficient to explain i, even if the value is value for i alone. I suspect that the ultimate fate of this strategy is no better than that of dispositional teleology, but there is at least a tradition here to give prima facie support. Rather, the fundamental problem arises here from (4). For (4) to obtain, i must in some way give itself a duty to obtain the value that e provides. But objects cannot have duties to themselves.[iii] In a manner similar to Wittgenstein’s private language argument and his comments concerning the standard metre, there is no distinction between the definition of a duty and the performance of it. Objects do not hold themselves accountable or even evaluate themselves in the performance of some duty. They merely act. To insist otherwise is to add some extra element to i that serves as the locus for evaluation. In this case, though, the value no longer belongs to i per se but to this evaluating part. The value of e loses its explanatory power in this way. So either axiological immanent teleology misses out on (4) (and subsequently also (3)) or it misses out on (5). In either case, axiological teleology cannot be immanent.
When we ask what makes teleology immanent, two options present themselves. But when neither can possibly obtain, we are forced to admit that immanent teleology does not obtain. This leaves us with only two options. Either there is no teleology at all or teleology is transcendent. I think that we should lean towards the latter.
[i] In practice, both Wiener and Wright ended up with accounts of axiological teleology despite their attempts to restrict themselves to bare dispositions. In the long run, this probably counts as evidence against a purely dispositional account of teleology. It seems that any moderately successful account of teleology has to import axiological considerations.
[ii] Some philosophers have taken this to be sufficient to be a refutation of inflationary accounts of teleology per se and propose a deflationary account in their place: the teleology we see is an appearance generated by an objects causal role in a system and nothing more. In essence, this is the foundation of the dispute between causal role and selected effect accounts of functions in the philosophy of biology. Both types of accounts are confused about the relevant metaphysics.
[iii] One might suggest the counterexample that people at least sometimes have duties to themselves. This is only possible because people are self-distinct. It is possible that one’s definition of a duty is distinct from the performance of it. That is, people are not metaphysical simples. But this entails transcendence, not immanence.