Aristotle on the ‘proper function’ of an object

Karen asked:

Part of Aristotle’s argument for his conclusion requires everything to have an ergon or proper function. How plausible is this claim when applied to natural objects?

Answer by Craig Skinner

The notion of a function applies naturally to artefacts: the function of a knife is to cut, of a printer to print, and so on. And Aristotle makes free use of the notion here, adding that a feature conducive to good function is a virtue e.g. sharpness is a virtue in a knife.

A ‘proper’ function is one peculiar to or characteristic of an object. A knife, for instance, could function as a poker or screwdriver, but cutting is its proper function.

What about extending the notion beyond artefacts?

The function of an artefact is built in by human intelligent design.

So if we think the natural world was designed (by God), then the idea of function can clearly be extended to natural objects.

However, Aristotle extended the notion to natural objects without assuming design: to inanimate objects, living things, and to humans and their institutions.

How plausible is this? The short answer is that extension to the inanimate relied on a now long-superseded physics and cosmology, and is of antiquarian interest only, whereas extension to the living world and to humans is insightful and fruitful if somewhat controversial.

I will deal briefly with each.

Functions of the inanimate: the proper function of heavenly bodies was circular motion; of elements (earth, air, fire, water), it was movement to their natural place and ordered transformation one into another. All this was a coherent system assuming the cosmology of the day, namely concentric spheres of differing densities centred on Earth. Thus the movement of the elements is a consistent theory of fluid mechanics. This physics and cosmology stood for two millennia but was decisively ousted by the geocentric cosmology and gravitational physics of Copernicus/ Galileo/ Newton so that Aristotelian cosmology, physics and associated notions of function applied to the inanimate are of historical interest only.

Functions of the animate: the difference between inanimate and animate beings was obvious to Aristotle (yes, these days we know of borderline cases like viruses, but leave that aside). A rock, say, doesn’t do anything, or have a goal, or act to maintain its stability and survival. A rook, by contrast, does things, gathers food, builds nests, cleans its feathers, lays eggs, all functions proper to its survival, health and reproduction. And we can extend the notion to the parts of an organism e.g. the function of the heart is to pump blood, the lungs to breathe in oxygen/breathe out CO2, the kidneys to clean the blood. And all these organ functions work together to facilitate the organism’s larger functions of survival and reproduction.

Aristotle of course included the human animal, which shares some functions with all living things, other functions with other animals, and has species-specific functions.

All of this was mostly uncontroversial for centuries. But it is tied in with Aristotle’s view of causation. This view is that explanation of something requires not only an account of what produced the thing (efficient cause) but also an account of what it is for (final cause) So, as regards a statue say, the efficient cause is the action of a sculptor, the final cause commemoration of a famous person. You can see that final cause is aim, goal or purpose (telos). And of course talk of function is much the same as talk of goal or purpose — the purpose of the heart is to pump blood, the goal of the rook’s flying around is to find food.

But then Descartes put the boot in.

Aristotle was a great biologist (his fieldwork in marine biology is at least as great as his writings on metaphysics and ethics), content to see function, goal and purpose everywhere in animate nature. Descartes, by contrast, was a great mathematician and physicist, greatly impressed by the new mechanical, corpuscular, philosophy, whereby one state succeeded another by necessity or natural law involving interaction of these corpuscles. In short he thought all causation in the physical world was efficient, mechanical causation, and declared that the notion of final causation was ‘useless in physics’. Later criticism of final causation accused it (unfairly) of entailing backward causation, and of positing conscious intentions in primitive organisms.

At any rate, thereafter, most philosophical discussion of causation was solely about efficient causation — think of Hume’s famous constant conjunction account, Kant’s transcendental argument for efficient causation.

Because of the link between function and goal (ergon and telos), and the disrepute telos fell into, some philosophers today are unhappy to admit that organisms/ parts have functions. Thus, they say, we claim the heart’s function is to pump blood, but it does other things, like making sounds (which doctors listen to), and we might as well say the heart’s function is to make sounds. By choosing the pumping rather than the noise option, we impose our idea of function on the world. I find this quite implausible. The pumping of the heart serves the needs/ends/functions of the organism, and without a pumping heart it dies, whereas the sounds produced are an inessential side effect — if mutation produced a variant heart that was quieter but just as good at pumping, this heart would function just as well as a heart.

I agree with Aristotle that full explanation includes final cause (what for?) as well as efficient cause (how come?). Of course we can give an account of any event purely in terms of efficient causes. Thus a rook’s flight (looking for food) is explained by certain brain states producing nerve impulses leading to wing muscle contractions resulting in flying here and there. But the story leaves out what it’s all for.

I recall a biology teacher asking my school class why polar bears are white. To camouflage them when they creep up on prey in the snow, we said. No, said he, it’s because bears in ancestral populations who happened to be white had a survival advantage so that, whiteness being heritable, succeeding generations included more and more, eventually all, white bears. Agreed, I said, but why was whiteness a survival advantage? Ah, because it afforded camouflage when stalking prey, admitted the teacher. You can’t get away from the teleological aspect of explanation.

Function of humans: we share the vegetative and reproductive functions of plants, and in addition the locomotive functions of animals. However Aristotle thought that the proper function of humans was reasoning: we are the rational animals. And the proper end for humans is a life of rational activity in accordance with virtue. His view of ethics with its emphasis on character and virtue (rather than on duty or consequence) saw a substantial revival in the 20th century — virtue ethics, as opposed to deontological or utilitarian ethics.

We could argue that other features than reason are peculiar to humans e.g. humour, genocide. But I feel that these either depend on reason or are an extension of functions seen in some other animals, and so Aristotle’s choice was a wise one.

I won’t deal with Aristotle’s views on the function of human institutions.

In conclusion I feel that Aristotle’s extension of the notion of function (ergon), intimately linked with purpose (telos), from artefacts to living organisms and humans, is entirely plausible and immensely fruitful.


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