On Laws and Ends: A Response to Hattab and Menn Dennis Des Chene Johns Hopkins University From the topics discussed by Hattab and Menn, I examine two of special im- portance. The ªrst is that of active powers: does the Cartesian natural world contain any, or is the apparent efªcacy of natural agents always to be re- ferred to God? In arguing that it is, I consider, following Hattab, Descartes characterization of natural laws as secondary causes. The second topic is that of ends. Menn argues, and I agree, that in late Aristotelianism Aris- totles own conception of an art in things has been abandoned. The point is reinforced when one considers the general divine ends which must be in- voked in cases of aborted action. In them no individual agent attains its end. Yet Nature as a whole continues to act toward ends. I suggest that those general ends, to which Suárez, for example, refers, may have served later philosophers, especially Malebranche, in combining the Cartesian notion of law with a teleological interpretation of nature that Descartes, for his part, rejected. In the transition from Aristotelian natural philosophymore speciªcally, that version which Menn calls liberal Jesuit Scholasticismto the mechanistic philosophy of the new science, two questions are of funda- mental importance in the explanation of natural events and our relation to them as knowing subjects and as agents. The ªrst is that of agency, the second that of the laws of nature. The Aristotelian philosophy takes natu- ral change to be the work of active powers in nature itself, in which God concurs. The Cartesian interprets it as the work of God alone, subject to natural laws, appeal to which will help demonstrate the observed regulari- ties which by the Aristotelian are referred to the intrinsic powers of mate- rial things, and to the ends toward which they act. By the question of agency, then, I mean in particular the question Where are the active powers that bring about change in the natural Perspectives on Science 2000, vol. 8, no. 2 ©2000 by The Massachusetts Institute of Technology 144 Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/106361400568055 by guest on 26 September 2021 Perspectives on Science 145 world? Hattabs paper, after discussing Descartes conception of force, de- votes itself to arguing that when he calls the laws of nature secondary causes, he should be taken at his word. It then explains how laws can be regarded as causes at all, and how they might occupy the role which in late Aristotelian physics was occupied by the active powers of natural agents. I remain, nevertheless, puzzled both by Descartes terminology and by the notion of laws as causes, and I will show why. The question of ends is yet simpler: Are there any? Or, more pointedly: Are there any ends other than those intended by rational agents? Certainly we conceive of some of our actions as directed to an end. We conceive of God likewise as having acted, in establishing the constitution of the natu- ral and human worlds, and in those particular interventions recorded in texts held true by faith, to accomplish various ends. In Physiologia I argued that for the Aristotelian philosophers I was concerned with, Aristotles own conception of ends as intrinsic to natural agents had become increas- ingly opaque. Another conceptionthat the ends of natural agents are in- tended by Godhad largely usurped its place. Adopting that conception, however, gave urgency to the problem of retaining for natural agents any genuine efªcacy. If art is no longer in things, but only in divine or human intellects, then natural agents seem to be reduced to instruments. That outcome, though welcomed by Descartes, was rejected by the Aristo- telians. On this, I think, Menn and I agree. We disagree on the interpreta- tion of Suárezs position, so I will do my best to clarify matters.1 1. Where is agency? The ªrst topic, then, is agency and active powers. For Aristotelians, in every natural change, there is an agent and a patient. The difference is real: it does not depend on our conception. Just as real are the powers by which agents act. The efªcient cause of a natural change is an agent designated from the point of view of the effect it produces in the patient, to which it 1. Since I have mentioned Aristotelianism several times, I will now exercise the au- thors privilege of retrospective revision. I should have emphasized more than I did in Physiologia that the Aristotelians in question are those that Menn calls liberal Jesuit Scho- lastics. Generalizations about Aristotelianism, even in the relatively brief period I exam- ined, must be either very broadly stated or limited in scope. Even among those who adopted Thomas Aquinas as their patron, there are major differences of opinion; the differ- ences grow all the greater if one takes in Scotists, Nominalists, or mavericks like Zabarella. Combining ideas from Ed Grant and Dan Sperber, I would take Aristotelianism to denote neither an essence nor a natural kind, but a massive and heterogeneous collection of con- cepts, methods, and doctrines endemic to the learned world of the period, which may be likened to a biological population (Grant 1987). Like inºuenza and other successful patho- gens it was easily transmissible and amenable to variation, and therefore capable of surviv- ing in diverse environment (Sperber 1996). Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/106361400568055 by guest on 26 September 2021 146 Laws and Ends gives, as all causes do, being. It brings into existence a quality like heat or even introduces a new substantial form into pre-existing matter. Unlike the material or formal causes the efªcient cause is extrinsic to its effect, even if per accidens cause and effect are identical individuals. That is far from the whole story, but it will do for now. The question at hand is: where is agency? In particular, do secondary causes have any efªcacy of their own, or are they instead like a carpenters saw, modulating the effects of the First Cause, but not themselves even the proximate principle of any action? It is agreed that God not only creates and conserves all other beings, but must allow, indeed co-operate with, their actions. Can a natural, nonrational, agent nevertheless beI quote here Suárezs version of the deªnitionthe ªrst principle from which there is an action, or again from which the effect exists, by way of an ac- tion (Disp. 17§1¶6; Suárez [1856] 1965, 25:582)? Descartes answer is No. That natural agents have no active powers whatsoever follows immediately from the deªnition of corporeal sub- stance or body as res extensa. If there are efªcient causes acting in nature other than God, they cannot be bodies. Descartes says that laws are causes, but ªrst one other candidate must be considered: force. Hattab has given a clear summary of the section in Physiologia where I sort out the interpreta- tions of Hatªeld, Gueroult, Gabbey, and Garber. From that discussion I arrive at what she calls a double-aspect interpretation of force. There is no one thing of which one can say both that it is a mover of bodies, an ac- tive power, and that it is measured by the quantity volume times speed. Volume and speed, and derivatively the product of the two, pertain to bodies; activity to God. In the case where a body at rest successfully resists a moving bodyas in Descartes fourth rule of collisionthe natural inertia possessed by every body, at rest or not, does not yield a force of resistance sufªcient to explain the outcome. The moving body can have any speed whatever; yet the body at rest, provided only that it is larger, will not budge. The usual factor measuring the conversion of the moving bodys quantity of motion into a quantity of motion in the body at rest, namely the ratio of the mov- ing bodys volume to that of the resting body, will not yield what Des- cartes wants. Instead the body at rest behaves as if it were part of some more inclusive body, as large as need be to compel the moving body to re- verse its course. From the standpoint of the smaller moving body, the force opposing its continued motion is effectively inªnite. In trying to grasp what Descartes had in mind in formulating the rules of collision, and considering the references to divine action in his argu- ments for the laws of nature, I suggested that we should think of the mov- ing force attributed to God as consisting in his concurrence, governed by Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/106361400568055 by guest on 26 September 2021 Perspectives on Science 147 those laws, in the changes that occur when bodies meet; but that the indeªnitely large force of resistance exhibited by some bodies at rest would be better referred to conservation. Hattab raises two questions. The ªrst concerns the parallel between static forces and conservation. I made two comparisons of this sort. One comparison, deriving ultimately from Bonaventura, is between conserva- tion and the force exerted by a nail, say, when it holds up a picture. This was by way of trying to understand how (as Gueroult believes) conserva- tion could be thought of as a force at all (Gueroult [1954] 1970). The other Ive just mentioned. Moving force is measured by volume times speed. But force of resistance, which as the force of a body at rest is in a sense static, is effectively inªnite.