By Brad Blue, April 6, 2011 in Uncategorized
In his Meditations on First Philosophy (1641), René Descartes criticizes (what he takes to be) the Scholastic conception of nature and final cause. Concerning nature, he writes:
“a clock constructed with wheels and weights observes all the laws of its nature just as closely when it is badly made and tells the wrong time as when it completely fulfills the wishes of the clockmaker […] Admittedly, when I consider the purpose of a clock, I may say that it is departing from its nature when it does not tell the right time […] But I am well aware that ‘nature’ as I have just used it has a very different significance from ‘nature’ in the other sense. As I have just used it, ‘nature’ is simply a label which depends on my thought; it is quite extraneous to the things to which it is applied […] But by ‘nature’ in the other sense I understand something which is really to be found in the things themselves.” (Sixth Meditation)
Nature in the sense of purpose is extraneous to things. According to Descartes, if we examine a clock, we will not discover that its purpose is to measure time. We will discover only how its parts move together according to the laws of motion. As Amy Schmitter comments, “the only properties we can find in the clock that enable it to serve any use lie in its configuration of parts. As such, the clock is properly understood as a configuration of extended parts, which happens to be pressed into service by humans, who manipulate it to serve an extrinsic end.” (“How to Engineer a Human Being: Passions and Functional Explanations in Descartes”) By analogy, the human body is properly understood as a configuration of extended parts, which happens to be pressed into service by God, who manipulates it to serve an extrinsic end.
What extrinsic end does God have in mind? According to Descartes, that question cannot be answered:
“[God] is capable of countless things whose causes are beyond my knowledge. And for this reason alone I consider the customary search for final causes to be totally useless in physics; there is considerable rashness in thinking myself capable of investigating the purposes of God.” (Fourth Meditation)
“When dealing with natural things we will, then, never derive any explanations from the purposes which God or nature may have had in view when creating them. For we should not be so arrogant as to suppose that we can share in God’s plans.” (Principles of Philosophy, I, 28)
We cannot know why God created man. That is, we cannot know man’s ‘nature’ or ‘final cause.’ All we can know is how man’s parts move together according to the laws of motion. The latter is man’s true nature, the nature that is really to be found in the thing itself.
Though we cannot know why God created man, we can still admire his handiwork:
“The function of the various parts of plants and animals etc. makes it appropriate to admire God as their efficient cause – to recognize and glorify the craftsman through examining his works; but we cannot guess from this what purpose God had in creating any given thing.” (Meditations, Fifth Set of Replies)
Descartes gives detailed descriptions, both in the Discourse on Method and the Passions of the Soul, of the functions of human organs. And he holds that “these functions follow from the mere arrangement of the machine’s organs every bit as naturally as the movements of a clock or other automaton follow from the arrangement of its counter-weights and wheels.” (Treatise on Man) Thus, the functions of the parts of man follow from his true nature.
It is curious that Descartes opposes purpose and function, and claims that the latter follows from the arrangement and motion of man’s parts, i.e., from his true nature. Someone familiar with Aristotle may wonder whether Descartes unwittingly adopts something like (or at least consistent with) the Aristotelian notion of natural teleology.
For Aristotle, there is an intimate relationship between form and function. The form or structure (eidos or morphe) of a substance enables it to do various things. Consider a Swiss Army knife (assuming it is a substance). It’s structure, the shape and arrangement of its parts, enables it to cut, screw, saw, etc. These are the knife’s functions. Thus, the form of the knife enables it to perform various functions. Put in the technical language of De Anima (see Book II, Chapter I), the knife’s first actuality (its form) produces a set of second potentialities (the things that the material is able to do in virtue of having the form of a Swiss Army knife). These second potentialities are themselves actualized when the knife is actually functioning, e.g., actually cutting or sawing. Such actualities are second actualities.
To talk of the form and second actuality of a substance is, for Aristotle, to talk about its nature and end (telos). The nature of a plant, for example, is its substantial form, its soul. And its final cause is the actualization of its second potentialities. What’s more, the latter follows from the former. The form or structure of the plant is what enables its function, the exercise of which is the plant’s end. In this sense, we can speak of the plant’s ‘purpose’: it’s purpose is to act in the way enabled by its form.
The question to ask of Descartes is whether his notion of function enabled by structure is sufficient to support a version of Aristotelian natural teleology. That question, in turn, figures in a larger one: Can the use that Aristotle makes of natural teleology as the foundation for ethics be made of Descartes ‘true nature’ and function? That is, can something like virtue ethics be founded on Cartesian physics?