A “match” that could not, under any circumstances, combust would not properly be a match. The intrinsic nature of such a “match” would not be causally aligned with the effect of combustion. A match, by contrast, is so constituted that its causal power naturally includes and aligns with the effect of combustion. Indeed, we understand what a match is precisely by understanding what it is for in the causal order. The match’s finality is tenuous, however, because it is an artifact, not a properly natural entity, so its finality is rooted more in the nature of the phosphorus on its head. Granted, numerous other random objects could cause combustion under immense speed and friction, but that would not merit calling them “matches” as well. Using such objects in a matchlike way would just be a different case (or species) of achieving a broader end (or causal genus). All such random objects would be artificially classed in terms of their combustible finality, rather than in terms of their material characteristics, and so even then their material potency would be ordered towards their formal finality.
Note well the contradiction that besets most critics of final causation. Even when they criticize the putative finality of a match (to use one, admittedly limited, example), they keep using that term as if it referred to one thing instead of any other. Why call “that little wooden” thing a match rather than a toothpick, or a large splinter? How do we know we’re all talking about the same thing––about the same causal factor––when we type the word “match”? We only know it because we implicitly agree on the causal link that exists between phosphorus-tipped wood, oxygen, and motion and the effect of fire. Absent this shared understanding of the causal link between matches and their effects, the entire debate becomes literally unintelligible.
Critics of final causality cannot, in one breath, reject an overriding finality for, say, matches and then, in the next, refer to the object in question based precisely on its use. The thrust of my opening paragraph was not to imply that the material elements which belong to matches can not be used for all sorts of other actions, but to emphasize the causal intelligibility that is inherent to matches qua matches. My aim was certainly not to aver that matches can never be used for some other end. But again, precisely by being used for some other end, they are being diverted from their original causal structure in order to fit within some other causal order. Just as an acorn that could never, under any causal circumstances, develop into an oak tree would be called a defective acorn, so too a match that could never, under any circumstances, result in the effect of combustion would not properly be called a match. A man may use a matchstick to gouge out his enemy’s eyes, but he still knows that he’s using a match to do that. How does he know that he used a match rather than a mallet to do the deed? He knows the causal powers that properly inhere in a match, even though he chose to tap into the causal powers of only one aspect of the match (i.e. its wood).
(I wrote the above in a thread at Doc Feser’s blog, in which he highlights a contemporary, non-Thomist’s defense of Aquinas’ account of final causation (PDF!).