«Descartes’ Mechanism and Biological Functions Abstract. The “new mechanical philosophy” takes its inspiration from biology and simultaneously ...»
Draft, 10/2013; Gideon Manning
Do not cite without permission
Descartes’ Mechanism and Biological Functions
Abstract. The “new mechanical philosophy” takes its inspiration from biology and
simultaneously traces its origin to René Descartes. It pays little attention to Descartes’
mechanistic biology, however, which, admittedly, even most historians of philosophy and
science mistakenly treat as a straightforward extension of Descartes’ attempt to explain natural
phenomena in terms of shapes and movement of parts. In this article, I discuss the status of biological functions in Descartes’ mechanistic philosophy. While avoiding the pitfall of misidentifying the parts of living things or the causal systems they constitute, I argue that Descartes’ mechanistic biology evinces a strong anthropocentrism both with respect to its goals and, more surprisingly, its metaphysical foundations. Today’s mechanistic biology is no longer anthropocentric, and it cannot embrace the metaphysical foundations Descartes proposes, but examining Descartes’ account of biological functions identifies problems any mechanistic philosophy must face that only his anthropocentrism allowed him to solve.
Keywords: Descartes, Mechanism, Functions, Teleology, Anthropocentricism
According to William Bechtel, the “new mechanistic philosophers of science,”— Machamer, et al. (2000), Glennan (2002), and many others, including Bechtel himself—have been inspired by biologists who, in their explanations, have long appealed to mechanisms as opposed to “theories or laws” (2011, pp. 536). The mechanist’s “core idea”, however, traces Draft, 10/2013; Gideon Manning Do not cite without permission back to René Descartes, who claimed to have described “the whole universe as if it were a machine” (AT 8A: 315, CSM 1: 279).1 Bechtel cites this much of Descartes to support his belief that Descartes explains “natural phenomena by identifying the responsible mechanism and explaining its functioning in terms of its parts and the operations they perform” (2011, pp. 535It is beyond dispute that the history of mechanism owes a great deal to biology and to Descartes, to say nothing of the Hellenistic physicians who, ultimately, were Descartes’ mechanistic inspiration. Rarely, however, have philosophers of science looked carefully at Descartes’ mechanistic biology. In particular, they have not considered whether Descartes’ biological explanations, which include many references to the complex causal structure of living things, are consistent with the new mechanical philosophy.
In this paper, I examine the biological functions Descartes identifies in an effort to bring together the two inspirations for the “new mechanical philosophy” (Bogen 2008). I begin by explaining Descartes’ vocabulary for “function” and the pluralism it implies. Next, I identify tensions between Cartesian metaphysics and Descartes’ concepts of biological function, noting in particular that Descartes’ well known rejection of teleology threatens to undermine both the evaluative standard he uses to assign functions and the unity he attributes to living things. I then evaluate positions available in the current secondary literature, notably those of Des Chene (2001), Brown (2012) and Hatfield (2008). Finally, I offer my own interpretation, which defends Descartes’ attribution of biological functions and explains how it follows from his broader metaphysical views concerning human beings. The guiding idea of my interpretation is that Descartes’ prohibition against teleology leaves room for biological functions and that Descartes is committed to a version of anthropocentrism that treats the human body as the model for all
of Descartes’ mechanism and highlights difficulties that even today’s mechanical philosophy must confront.
2. Cartesian Pluralism.
There are two concepts of function operating in Descartes’ work. Appreciating this fact, we will immediately advance beyond many recent interpreters who, by failing to attend to Descartes’ pluralism, handicap efforts to understand his biology. In this section I discuss each concept separately and then indicate how the two relate to one another.
2.1. Normative Functions.
Descartes attributes what I call normative functions (NFs) to the parts and activities of living things. He writes, for example, about “the true function [usage] of respiration” and “the main function [usage] of the lung” (AT 6: 53, CSM 1: 138; AT 11: 236). Descartes even commits himself to the then-standard view that the “function [usage] of each muscle” can be learned through anatomical study (AT 11: 138).2 In each case, when he speaks of a “true” or “main” function, he is telling us what a thing is supposed to do.
To gain greater insight into this first concept of function, it is worth noting that usage, and the Latin usus from which it derives, have a well defined evaluative connotation in the life sciences of Descartes’ time.3 They answer the question, ‘what is this part or activity good for?’ by specifying a good or benefit that a part or activity provides to or for a living thing.4 Descartes explicitly links usage with utilité—that is, “benefit” or “usefulness”—when he writes, the
CSM 1: 349). And, as he immediately clarifies, it is not “the objects which stimulate the senses [and] excite different passions in us” that primarily concern us, but rather “the various ways in which [the objects] may harm or benefit us, or in general have importance for us.”5 When Descartes attributes functions in this first sense, he is specifying what benefits an animal ultimately derives from a given part or activity. I address how this determination is made in Section 2.3 but, preliminarily, it is important to see that Descartes is assuming an evaluative standard that a part or activity is supposed to meet: it is supposed to benefit a living thing.
Whether he is justified in this is one of the central topics for interpreters of Descartes’ biology, yet it is only by looking for normative properties—the value a thing has to or for a living thing— that he can specify the “true” or “main” function of a part or activity.
2.2. Causal Functions.
Another concept of “function,” what I will call “causal functions” (CFs), appears whenever Descartes uses the French fonction and the Latin functio and actio. Like usage, these are technical terms in the early modern life sciences.6 They answer the question: how does this part or activity work? Effectively, these are the functions identified by Cummins (1975), for a CF tells us how or what, as a matter of current fact, a certain part or activity contributes to the production of a given phenomenon or capacitiy. No evaluative standard—and nothing normative—is implied by Descartes’ fonction, functio or actio. They merely describe what some part or activity currently does or is disposed to do.
There are many instances in Descartes’ biology where he attributes CFs—so many, in
I hypothesize the body to be nothing but a statue or machine.... [with] all the parts required to make it walk, eat, breathe, and indeed to imitate all those of our functions [fonctions] which can be imagined to proceed from matter and to depend solely on the disposition of the organs. (AT 11: 120, CSM 1: 99; modified) [I]f only we had spent enough effort getting to know the nature of our body, instead of attributing to the soul functions [fonctions]which depend solely on the body and on the disposition of its organs.... [F]unctions [fonctions] which some people attribute to the soul, such as moving the heart and the arteries, digesting food in the stomach and so on,
do not involve any thought, and are simply bodily movements. (AT 11: 224-5, CSM 1:
314-315) These are programmatic statements. Walking, eating, breathing, cardiac motion and the pulse all causally depend on some disposition of the parts of the body. There is no claim of benefit in the texts above. In fact, fonctions could just as easily have been translated “actions,” “movements” or even, simply, “effects,” without losing Descartes’ meaning. The latter passage makes this very claim.7
2.3. Functions, Medicine and Malfunctions.
NFs and CFs offer answers to distinct questions and draw on different facts about living things. Nevertheless, it would be a mistake to think the two are unrelated, or that they represent
with their own bodies, including, e.g. their hands, which are good grabbing—or the CF of a part while remaining ignorant of what it is good for—this describes the state of most mechanistic biology, which either avoids speculating about what a thing is good for or, as in the case of the appendix, for the longest time has no idea of its NF—but Descartes’ biology is not content with either alone.
Consider the example of the heart. For a fairly wide range of biological phenomena that we now seek to explain, everyone agrees that the heart’s CF is to pump the blood; pumping leads to circulation, which, in turn, makes possible a host of other CFs. Descartes could not be more committed to this claim which, at the time, had only recently been proposed by William Harvey.
Descartes goes so far as to say that failing to correctly identify the heart’s CF “we cannot know anything regarding the theory of medicine, because all the other functions [fonctions] in the animal depend on the heart” (AT XI: 245). So, for example, if we are interested in explaining the capacity of an animal to deliver nutrients to its cells, we will discover that the heart’s CF is to pump blood. If we are interested in explaining the capacity of an animal to flee from predators, we will discover that the heart’s CF is to pump blood. In each case, a higher level or subsequent effect or capacity can be traced back to the activity of the heart as its cause. Ergo, as seen from the perspective of the biologist interested in explaining nutrition and animal motion, the heart’s CF is to pump the blood.
It is certainly conceivable that Descartes could have stopped here, in which case his biology would limit itself to explaining how the body and its parts work on the assumption that certain effects and capacities are uniquely biological. But Descartes’ willingness to identify the
phenomenon, like nutrition or movement, but that it should produce that effect; that producing this effect is its “true” or “main” function regardless of what it is actually doing now. In spite of the examples of NFs in Descartes’ biology, several recent interpreters deny that Descartes actually meant, or that he is entitled, to attribute NFs to the parts of living things.
This issue interpretative dispute will be explored further in Section 3.1, but I want to suggest, preliminarily, that such conclusions come at a much higher cost than any of their proponents acknowledge. Indeed, without NFs, Descartes cannot attribute malfunctions to the parts or activities of living things, in which case his effort to unify the sciences unravels. For Descartes organizes the disciplines on the model of a tree (AT 8A:14-15, CSM 1: 186-87). He calls the roots “metaphysics,” the trunk “physics,” and “medicine,” along with other applied sciences, are the limbs where the “fruit” is borne. Medicine’s foundation in biology is explicit in this organization of the disciplines, where biology exists somewhere between physics and medicine.8 If medicine’s aims are to be realized, physicians committed to deriving their principles from biology must be able to use biological functions to make assessments of the human body’s healthy and diseased states; Descartes’ biology must differentiate between functions and malfunctions. For physicians to know when to intervene, they must know not only how things work—their CFs—but what a thing’s function is supposed to be—its NFs—so that they can set it right. We should not discount NFs precisely because Descartes recognizes that CFs alone are insufficient to link biology to medicine.9 Indeed, Descartes does attribute NFs in his biological works, acknowledging them whenever he can tie a CF to a living thing’s preservation. Preservation in this case is not simply
CF is a means of securing preservation, than we know what the part or activity having that CF is good for, and Descartes will say it has an usage.
It is important to note that only those CFs strictly necessary for the animal’s preservation are termed “true” or “main” NFs, which indicates that a part of activity can have a number of CFs and NFs. Descartes writes, for example, that the “main function [usage]” of the lung is to take in air and alter the blood in transit from the right to the left ventricle. It is the lung’s immediate effect of altering the blood that enables the heart to pump blood. Yet, jarringly to the modern reader, the lungs have the “other [normative] function [usage]” of taking in air to “produce the voice” (AT 11: 236). Of these NFs, only the “main” NF of the lung is a CF strictly necessary for the animal’s survival. The voice may be beneficial in a great many circumstances, but for Descartes it is not strictly necessary.10 Elsewhere, focusing on respiration, Descartes tells us that its “true function [usage]” is to “bring enough fresh air into the lungs to” cool the blood (AT 6: 53, CSM 1: 138). Failing this, the “blood would not be fit to serve as fuel for the fire without light in the heart.” Descartes’ point is that respiration’s “true” NF is to support the heart’s CF of pumping blood. Like the heart’s CF of pumping blood, the respiration’s CF of cooling the blood is strictly necessary to assure the animal’s preservation. It is only in relation to this final effect, to preservation, which for Descartes’ biological and medical purposes is an unquestioned good, that a CF’s normative properties reveal themselves.
Key to my reconstruction is the claim that preservation is the final effect in terms of which Descartes evaluates CFs. This will be no less controversial than Descartes’ attribution of NFs themselves, and I will return to it in Section 5.2, but the claim itself is supported by a