This is only a problem if we suppose that each species has a corresponding essence- and the ancients did tend to speak this way -but this needn't be so. I suspect that the typology of life is actually far more complicated and that while there are shared essences they don't really cleanly divide along species lines. Life has forms in the way clay has form which are sculpted by various processes of descent. These are, indeed, real forms, but they are not the naive forms of common classifications.

It's worth drawing the distinction between properties and kinds (essences) here:

Incessable wrote:

I think, nominalism works much better with modern evolutionary theory than Aristotelian realism (or Platonic realism); dogs and cows are part of a continuum of individual descent, we've assigned names to particular points in this continuum, and when we ask "what is this?" we are really just asking "which of our named points is this closer to?"; finding some equidistant medians between our named points is then no real problem.

Most moderate realists these days are property realists, not kind realists.

Non-trope nominalism about properties never really recovered from Armstrong's attack. Rodriguez-Pereyra wrote a respectable defense of resemblance nominalism, but he ends up needing to adopt David Lewis's extreme modal realism.

Bill McEnaney posted an article on essences and evolution a couple weeks ago.

I find it difficult to reconcile evolution with a denial of essence, because evolution presupposes an essential disinction between living species; otherwise, it would not be meaningful to claim a new species arises.

Speaking of a dogcow is like speaking of a square-circle. The thing is impossible and certainly distinct from either a dog or a cow. Chimeras are conceivable (and imaginable) exactly insofar as they are some part of them like one animal and like another; but the conception and the imagination both presuppose a difference. For example, what is it to say (or imagine) some animal has the leg of a cow and this same leg, at the same time, is the leg of a dog? It cannot be. It is perhaps both conceivable and imaginable that some animal looks like a dog but behaves like a cow or looks like a cow but behaves like a dog; however, it cannot be both at the same time (it cannot look like a dog and a cow at the same time or behave like a dog and cow at the same time).

Of course, what evolution effectively implies is that all living things are only accidentally different. This is ridiculous, however, because (e.g.) vegetative life is not sentient and doesn't have the sentient desires and appetites of an animal. They cannot be merely accidentally distinct beings; otherwise, plants become animals and animals, plants. A dog, then, is not really distinct from a shrub. But who would be so silly as to treat a poisonous snake as they would a trained and domesticated dog?

Last edited by Timocrates (3/14/2016 10:01 pm)

Other quite plausible possibilities to retaining the notion that there are natural species of living things:

(1) There are many more biological than natural species. I am fond of Aristotle's three (plants, animals, humans (include Vulcans, dolphins - whatever other rational animals there may be). Or the familiar division of animals into avians, mammals, fish etc.

(2) Detune 'natural' from 'eternal'. Allow that natural species of all kinds can come and go. If Big Band theory is correct, there was a time when even the proton, or gold, did not exist.

(3) Detune 'natural' from 'fixed'. Why can't some natural essences morph one into the other? (That's not a rhetorical question.) Maybe e.g. squirrels are *not* supposed to perfectlty reproduce. They would not be very adaptive, and adaption is important to life on Earth.

(4) Distinguish pre-lapsarian from current Nature. Fallen things don't perfectly reproduce themselves.

(5) Make an epistemic move: it's common in scholastic thought to claim there are essences, but deny we have much access to them except perhaps our own. Ex: think the difference between natural 'roundness' for a planet, and 'sphere'; spheres are a lot like the round things of Nature, but none of them are exactly spheres. I always thought we didn't even know - we didn't strictly have *scientia* - of even humble things like cats. There's an infamous (to me) passage in Metaphys. I.1 where Aristotle as good as notes that science exists, but we don't have it, and can't - then just moves right on as if to say 'but we're gonna do it *anyway*, boys.' Our sciences only approximate their subjects' essential natures.

(6) Allow that Creation still is working itself out; allow that God may not have fixed exactly how it plays out As if it were, er, um, pardon the humble metaphor, but like a Dungeons and Dragons game. The Dungeonmaster only sets certain parameters and adjudicates, brings up encounters with key non-player characters, and occasionally intervenes personally; but the players make all kinds of things happen that are, if not Creative, then sub-creative, or innovative. Perhaps 'eukaryote' was necessary, but 'mammal' was not; or 'mammal' but not 'cow'.

Chris-Kirk

Last edited by Shade Tree Philosopher (3/16/2016 11:49 pm)

I don't know about current scientists, Timocrates, but Darwin in his "Origin of Species" saw that categorization not as intrinsic but as arbitrary in the end, and he saw it as an implication of his theory.  He denied the idea of species as something real to organisms.  The idea of species was more as a useful way for us humans to categorize life that is "different enough" in contrast with the different variations of organisms that differ only slightly from each other.  The difference between actual speciation and that of mere variations was a difference of degree and not of type.