Homo est ...

What is a man? If we ask a chemist, he'd say, 'Oxygen, carbon, hydrogen, nitrogen, calcium, phosphorous ...' But that is what a man is made of micro-materially. And we want to know what a man is formally. What is man's whatness (quidditas)? That's the question. The traditional answer is: animal rationale. The early-modern answer is: res cogitans. The late-modern answer is: res extensa. Thus Richard Dawkins says today that we are machines for replicating deoxyribonucleic acid. (And even then he has contradicted his dysteleological premises. Thereon we are machines for replicating that replicate DNA — we aren't really for anything.) But in reality we are not machines at all. And although 'rational animal' may not be the best possible definition, it hasn't been bettered. It's still the best we've got, after millennia. And it's everything a definitio rei is supposed to be: clear, terse, literal, positive, noncircular, and extensionally sufficient.

For Notker Labeo of St. Gall, homo est animal rationale, mortale, risus capax. For Wittgensteinians such as Sir Anthony Kenny and P.M.S. Hacker, man is most of all the talking animal, homo loquens. For the Princeton theologian Robert W. Jenson, man is more so the praying animal, be that prayer praiseful or maledictive (see vol. II of his systematics, pp. 58-9). Elsewise man is the weeping animal, the dancing animal, the smiling, blushing, ironizing animal. And to say as much is at least understandable. For brute animals do no such rationalised things, save by analogy (now more, now less remote). But these are bad definitions. Definitions are made of formal genera and species. And it is agreed that man's proximate genus is animal. But a particular proprium (e.g. talking, à la Kenny and Hacker) can't rightly be the specific difference. And likewise for selections of propria (e.g. moralising and laughing, à la Notker). We need an ontological antecedent that explains the countless consequents. Hence rationality. Homo est animal rationale—full stop. We talk, we moralise, and so on, because we are rational, (not the other way around).

But don't, say, chimpanzees also smile? No, not literally. That is, if we say 'Humans smile and chimps smile' then the verb isn't anymore univocal. Milton was right: 'Smiles from reason flow | To brute denied ...' (Paradise Lost, IX.239). The toothy grin of a chimp cannot literally be called a smile, for there is a rational intentionality present in the latter (and absent from the former). And so, however similar the bodily mechanics may be, brute grins are never more than simulacra of smiles. (Cf. the pathological risus sardonicus.) Thus Wittgenstein: 'A smiling mouth smiles only in a human face' (Philosophical Investigations: 583). To say that chimps smile is to anthropomorphise. And, no, there's nothing per se wrong with such anthropomorphising, so long as we remember that's what we're doing. From childhood up, we all of us animate inanimates (a metal tool 'groans' as it is bent from misuse); we animalise vegetables (a dry plant is 'thirsty' for water); and we humanise animals. So long as we are moving ontologically upward, it's a psychologically healthy thing to do. (If somebody moved downward, vegetablising animals, then we'd be worried.) But animating inanimates and humanising nonhumans is not something that scientists qua scientists may do (licitly). For it is no more literally(-univocally) true to say that brutes 'smile' (or whatever) than it is to say that rocks reproduce (because they break up into multiples).

Side-note: Here we have a serious bioscience problem, that of untranslatable metaphors and anthropomorphisms. Bioscientific terminology is through-and-through figural (and therefore through-and-through unscientific). Take so-called natural selection. The term selection is already a very misleading anthropomorphism. And in Darwin's Origin of Species metaphors hugely outnumber literalisms. (Therein natural selection is said to 'pick out with unerring skill,' it is 'always intently watching,' and so forth. It's practically a hands-on demiurge.) Darwinian evolution is supposed to be a nominalism and a dysteleogism, too, but there are realisms and teleogisms on every page of every book written by Darwinists. And it's worrisome that strictly literal translations aren't ever forthcoming. Is it even possible, we may ask, to reduce teleologies to efficiencies? Would such a translation be at all readable? Whenever a bioscientist tries his hand as literalist, he fails flatly, (elsewise he succeeds in drafting a reductio ad absurdum for his mechanically reductionist premises).

Summa. We are rational animals. And 'rational animal' is an infima species.