Kevin,

You’re right about the origins of St. Thomas’s Third Way. In On the Power of God, a work dated after the Summa contra Gentiles but before the Summa Theologica, he explicitly attributes the argument to Ibn Sina, with developments added by Ibn Rushd. (In fact, all of the arguments used in the Five Ways are explicitly attributed to other philosophers at some point or another in St. Thomas’s work.)

You wrote: What is “Thomistic”?

Of or pertaining to the thought of St. Thomas Aquinas, a Doctor of the Church and the leading figure of the revival of Aristotelian philosophy during the High Middle Ages.

St. Thomas famously believed that, although many of the mysteries of Christian faith could not be discovered by natural reason, and had to be revealed by the grace of God, there were at least some doctrines of natural theology, and in particular, the existence of an uncaused, necessary, and perfect Creator of the visible world), which could be proven through rational demonstration, and set out his Five Ways to prove the existence of God. The third of the Five Ways, the argument from possibility and necessity, is intended to demonstrate that there must be a single necessary being — i.e. a being which could not possibly fail to exist — to explain the existence of contingent beings — i.e. beings which do exist, but could fail to exist.

Kevin’s right about the origins of the argument; in an earlier book, Aquinas explicitly attributes the development of the argument to two Muslim commentators on Aristotle — the Persian philosopher-physician Ibn Sina (known in Europe as “Avicenna”) and the Spanish-Arab philosopher Ibn Rushd (known in Europe as “Averroës”). Generally speaking, a lot of the revival of Aristotelian philosophy in Christian Europe during the High Middle Ages was deeply influenced by the work of Muslim scholars a century or two before; indeed, without the texts that Arab scholars preserved and copied, the renewed interest in classical Greek learning in Christian Europe would hardly have been possible: most of the work of Plato and Aristotle, among others, had been completely lost in Western Europe for hundreds of years, until Muslim scholars re-introduced it.

Hope this helps.

William H. Stoddard: The trouble with this sort of argument, though, is that it treats the legal term “animal” as synonymous with the biological term “animal.”

Well, I stipulated that I was considering the term as “used in contemporary English,” by which I mean ordinary English rather than a particular technical argot. If I were a wagering man, I’d wager that in most ordinary contexts of use “animal” is a deferential term in which non-specialists defer to biologists (not lawyers) for the referent-fixing criteria.

William H. Stoddard: Though whether Superman is nonhuman seems debatable. There’s lots of material from DC that suggests that he and human women are interfertile.

But I don’t think that being interfertile with human beings would make Superman human, or a member of the biological species H. sapiens. Species are constituted (among other things) by their common evolutionary heritage, which Superman — who has an unrelated alien lineage — does not share. (You can hybridize peaches, plums, and apricots; but that doesn’t make them all members of the same species.)

Roderick: If Superman doesn’t count as an animal because he’s not biologically related to homo sapiens, then perhaps Lois Lane doesn’t either, because homo sapiens is the name for a species in our universe whereas Lois Lane lives in the DC universe and is not biologically related to anybody in our universe.

Well, if homo sapiens names a natural kind, surely it names the same natural kind in every possible world, and in a given possible world W it is only the case that humans in W have to be related to all the other humans in W, not that they have to be related (how?) to humans in other worlds not actual relative to W. In order to prove that there are at least some humans in the D.C. universe, you just need to find at least one actual human who exists in the D.C. universe as well as in @. Any such must also be human in the D.C. universe as well as in @ (since humans have humanity essentially, not accidentally). There are in fact plenty of cases of transworld identity (e.g. Franklin D. Roosevelt and Adolf Hitler have both appeared). So as long as it’s part of the story that Lois Lane et al. are appropriately related, evolutionarily speaking, to these known humans, Lois Lane et al. will also count as members of the human species.

Black Bloke: Nivens ignored a lot of things for the sake of comedy.

Too bad, I guess, since the essay is not very funny.

Etymologically, “bestiality” would seem to be best defined as “sex with a beast,” i.e. a nonrational animal. So I think Lois is O.K. to the extent that Supes counts as rational.

On the other hand, I’m not sure that he counts as an animal at all — at least, as the term is used in contemporary English. Your argument seems to presuppose that it’s the name of a functional or structural kind, rather than the name of a particular biological kingdom. If it’s the latter, then the natural kind can’t include anything that’s not interrelated with the other members of the kingdom, meaning that, except on a theory of panspermia, no alien life form at all could count as an “animal” except in a scare-quoted, analogical usage.