Chapter 5: Feser v. Molière
In Molière’s play “Le Malade imaginaire” (The Imaginary Invalid or The Hypochondriac), there’s a scene between an oh-so-pretentious doctor and an equally pretentious medical student. The doctor asks the student, in dog Latin why it is that opium causes sleep. The student replies that opium has “virtus dormitiva” (Latin for “sleeping power”) which has the power to cause sleep. In other words, it causes sleep because it causes sleep. But if you say it in Latin, it sounds like an explanation.
Feser explains why this is an unfair characterization of Scholastic thought:
whatever the specific empirical details about opium turn out to be, the fundamental metaphysical reality is that these details are just the mechanism by which opium manifests the inherent powers it has qua opium, […] The empirical chemical facts as now known are nothing other than a specification of the material cause underlying the formal and final causes that define the essence of opium. [p. 181]
In other words, opium causes sleep because it has such-and-such chemical characteristics, and these characteristics in turn are just the implementation of opium’s power to cause sleep, a power that is part of opium’s essence. That’s part of what makes it opium; opium without somniferious powers wouldn’t be opium.
According to Wikipedia, opium is latex derived from opium poppies. One of its most important components is morphine, originally named after Morpheus, the Greek god of dreams, for its sleep-inducing properties. As far as I know, it works by binding to opioid receptors in the brain and triggering a cascade of biochemical reactions in the body, one effect of which is sleep.
The important part here seems to be that it binds to specific receptors in the brain. That is, some part of the morphine molecule has the correct shape to align itself with its matching molecules in the brain. Even if this explanation isn’t quite right, I hope it’s close enough for jazz.
So let’s imagine that we’ve managed to extract the morphine from a bottle of opium, and we’ve put some into a brownie or other foodstuff, so that if someone eats the laced brownie, they’ll fall asleep.
I think Feser would say that the bottle contains corrupted or denatured opium: it still has “sleep-inducing” as part of its essence, but due to tampering by humans, this feature can no longer be expressed (in the same way that a brain-damaged person retains the essence of a rational animal). The morphine is really just the implementation of opium’s sleep-causing essential property, and we’ve broken this implementation.
And on the other hand, we have a corrupted brownie, or at least an altered one: even if there’s nothing in the brownie essence about causing or preventing sleep, we now have a brownie that does cause sleep. The sleep-neutral essence remains the same, but the implementation does cause sleep.
So by moving a chemical, morphine, from A to B, we’ve “moved” the sleep-causing property from A to B, regardless of what their respective essences are. So “essence” doesn’t seem to be a useful concept, here. If we want to know whether some entity X will cause sleep (and that’s an important of the essence of opium, remember), we’re better off asking whether X contains morphine than whether X has a sleep-causing essence.
How, exactly, does “essence” help us figure out how the world works? How do we determine something’s essence?
What makes a human being a rational animal, on the Aristotelian view, is not that he or she actually does or can exercise rationality at some point or other, but rather that an inherent potential for the exercise of rationality is actually in every human organism in a sense in which it is not in a turnip, or a dog, or a skin cell. […] And yet an immature or damaged human being is still a human being, which entails that it has the form of a human being and thus the potentials inherent in that form, whether or not they are ever actualized. [p. 182]
I think we can all agree that the term “human being” covers a wide variety of entities, including men, women, infants, centenarians, and much variation besides. And we can also, I think, agree that a bundle of HeLa cells is not a human being, even though each such cell has human DNA, and traces its ancestry back to one specific person who was unquestionably human. That is, some distinctions matter, and others don’t: there are many differences between Anne Frank and Nelson Mandela, but they’re small enough that both of them count as full-fledged human beings. The differences between Henrietta Lacks and a HeLa cell, on the other hand, seem big enough that it seems worth having different terms for the two. Or, as Feser would probably say, Henrietta Lacks and HeLa cells have different essences. The multi- vs. unicellularity, the presence or absence of individual organs, seem to make this a good joint at which to carve nature, to use Plato’s phrase.
Feser seems to think that nature is all joints; that everything falls into one category or another, and that these categories are natural and objective. That’s why he’s adamant that a newly-fertilized egg is as much of a human being as a thirty-year-old woman. He doesn’t seem to accept that we humans ultimately decide where we want to draw boundaries between categories, or even whether we want to draw boundaries at all. But if natural, objective boundaries were there, presumably there wouldn’t have been any argument over whether Pluto is a planet. Instead, astronomers agreed on the physical characteristics of Pluto and the other planets — their mass, size, position, velocity, sphericity, chemical composition (approximate), and so forth — and disagreed over which criteria ought to be used to classify something as a planet.
So yes, there are joints at which to carve nature, but they often depend on what we’re trying to do: if you were a pet store clerk and had a blind kitten – an entity that’s just like an ordinary kitten, aside from being blind – this one difference seems small enough that you could still find someone to adopt it. But if you had an entity that’s just like an ordinary parrot, aside from being dead, that one difference seems much more of a deal-breaker.