NEH SEMINAR I: EXTENSION, INERTIA AND ORGANIC SYSTEMS

Transcription

1 NEH SEMINAR I: EXTENSION, INERTIA AND ORGANIC SYSTEMS PART 1: 1.1. Problems for mechanistic biology: 1. The growing paradox. If a body is a determinate part of matter, then it doesn t grow. But Flossie the cow grows, and Flossie is a body whatever else she may be. 2. Functional analysis. Two questions: (i) What is a function if not a function for some particular end? (ii) What is the relationship between the functional and micromechanical levels of analysis? (Is this reductionism?) 3. What is the metaphysical status of an organism? 4. What s this thing called life? Is there any significant difference between living and non-living bodies? Is artificial life is a possibility? 5. Is animal or machine intelligence is a possibility? 1.2. The growing paradox I do not think that there is any part of our members which remains the same in number for one moment alone; still our body in as much as it is a human body remains always the same in number while it is united with the same soul. And even in this sense it is indivisible for if one cuts off an arm or a leg from a man we will say that his body is divided taking the name body in the first signification but not taking it in the second. And we do not think that someone who has an arm or leg cut off is less a human than any other. (AT IV, 167.) Fine for humans but what about other organisms? Of the four senses of unity Des Chene has identified in Descartes corpus none, he argues, can be applied to organisms. Substantial unity applies only to bodies united to a substantial form. Any part of matter can be considered a substance body in general (corps en general) or a determinate part of matter. From this perspective a body just is a collection (ensemble) or quantity of matter, any change in the quantity of which signals a change in the substance (Pr II.8). Physical unity refers to a determinate part of matter that moves together (Pr II.25). Dispositional unity by virtue of having the same arrangement of matter over time can tolerate small changes in quantity. But it is arbitrary to pick out which arrangement and which activity constitutes the organism unless we appeal to design intentions. Functional unity also implies design intentions. There is no identifying proper functions in the absence of specifying what a function is for Unity of composition: we understand how the parts of an animal are unified by reference to the whole animal of which they are a part. Notice that if we have different ideas of two things, there are two ways in which they may be taken to be one and the same thing: either in virtue of the unity and identity of nature, or else merely in respect of the unity of composition. For example, the ideas which we have of shape and of motion are not the same, nor are our ideas of understanding or volition, nor are those of bones and flesh, nor are those of thought and of an extended thing. But our perception is different in the case of the thing that we consider under the form of bone and that which we consider under the form of flesh; and hence we cannot take them as one and the same thing in virtue of a unity of nature but can regard them as the same only in respect of unity of composition i.e., only in so far as it is one and the same animal which has bones and flesh. (CSM 2:285-6; AT 7:423-4) The categories of bones and flesh are functional categories and their being defined in terms of their relations to the whole animal suggests that the unity of composition depends on the functional integration of parts.

2 Examples: In the Meditations the functions of sensations and passions are defined by their contribution to the conservation of the healthy human. [AT 7: 87 88] The Passions of the Soul offers a finer-grained account of these functions, relating them to the body, the soul, and the whole human being. [AT 11: 331-3; 342; 351; 359] The organs of the human body are defined by their functions: that which we call, for example, the arm or hand of a man is that which has the exterior shape, size and use of one. [AT 4: 169; my emphasis] The Treatise on Man and Description of the Human Body explicate the functions of the parts and physiological processes of the human body without reference to an animating soul. [AT 11: 199ff; 223ff] The organs of animals and proper parts of plants are also subject to functional analysis. [AT 7: 230; AT 4: 573 6; AT 5: 276 7] I desire, say I, that you would consider that these functions all follow naturally in this machine solely from the disposition of its organs, neither more nor less than the movements of a clock or other automaton [follow] from those of its counterweights and wheels, with the result that it is not at all necessary to conceive for their operation any other vegetative or sensitive soul in it or any other principle of movement and life than its blood and spirits, agitated by the heat of the fire which burns continuously in its heart and is in no way of another nature than all the fires that are in inanimate bodies. [AT 11: 202] 1.4. Two problems for the functional unity reading: (i) Organisms are not substances. If they are in the category of modes, of what are they modes? (ii) Is it possible to read function in Descartes in naturalistic terms? 2. Functions: Three interpretations of Descartes functionalism: (1) Projectivism: Des Chene (2011, 11): Cf also: Rorty. (2) Naturalised Teleology: Hatfield (2008, 413): end-state selected teleology not endstate caused teleology. (3) Causal functional analysis. (Brown 2012) 2.1. Finality in the Aristotelian tradition: Aristotle defines his account of finality in nature in the Physics in opposition to ancient materialism. They rejected natural teleology on the grounds that (1) if natural necessity is true, then things will happen as they do regardless of any end; (2) sometimes things have a good outcome, sometimes a bad outcome, which are contradictory; hence, things happen neither for the sake of the one nor the other; and (3) what does not deliberate does not act for the sake of an end, and no other things besides humans deliberate. (Physics II.8.198b17-23) Rejecting these arguments, Aristotle appeals to the regularity and order of nature, citing biological examples, which, he claims, can be explained neither in terms of efficient causality alone nor as the product of chance. Each stage of a plant s growth is both an end of a previous stage and for the sake of the next, and ultimately for the sake of the nourishment and reproduction of the plant. (II.8.199a20-30) At one point Aristotle identifies the form as that for the sake of which a thing develops or is done. (II.8.199a31-33) It is to realise its specific form that a plant sends roots down and shoots up Problems: 1. Causes are necessarily prior to effects, but the end is not prior. It is argued that nothing is cause of nothing; but that fire to be generated is nothing when that heating exists, that health is nothing when the doctor operates in that way. Therefore, that fire or that health are not causes of the things mentioned. [John Buridan, Quaestiones libri physicorum, Bk. II. Q.7] Some medievals subsumed final causality under the design intentions of God. For Aquinas, the natural inclinations or natural appetites of bodies derive from their substantial form and are subordinate to the (cognized) intentions of God. (De principiis naturae, ch.3; S.T, I, q.80.a. 1.; De Veritate, q.5, a.2 & q.25, a.1)

3 2. Identity of activities: if an activity (e.g., web building) is interrupted, what activity is it? 3. Monsters: if generation is for the sake of reproducing a form and the form comes to exist in matter and matter is nothing but for form, what accounts for the failure in the purposive effort? Descartes objections: 4. God s intentions are prior to their effects and so no different from efficient causes. (CSM 1: 202; AT 8A: 15-16) 5. It is hubris to pretend to understand God s purposes. (CSM 2: 38-9; AT 7: 55; see also AT 8A: 81 & AT 4: 292) 6. Things can only act for ends if they are capable of representing those ends to themselves, which in the case of bodies would be absurd. Cf: Descartes rejection of the Scholastic account of heaviness (gravitas). (CSM 2:298; AT 7:442; AT 3: 667-8;) 2.3. Descartes positive account: The rules of mechanics suffice to explain all the behaviours of bodies, including animals. (CSMK: 155; AT 3:213) However, Descartes rejects chance as a cause. Behaviour of corpuscles is governed by the laws. (CSM 1: 380; AT 11:438) Gassendi, More, Cudworth, Highmore, Conway, Malebranche, Cavendish: all think that mechanism is too impoverished to explain the order and regularity of organic nature. Gassendi and Malebranche appeal to God s intentions; More, Cudworth, Conway and Cavendish are attracted to vitalism Naturalised Teleological reading: At Physics II.8, 198b28-32 Aristotle cites (but does not seriously consider) the ancient materialist s response: Whenever then all the parts came about just what they would have been if they had come to be for an end, such things survived, being organized spontaneously in a fitting way; whereas those which grew otherwise perished, as Empedocles says his man-faced oxprogeny did. Hatfield [2008: 413]: Where a previous tendency to produce a certain end-state causes a type of thing or mechanism to exist now there may we ascribe a function. 3 Problems: (i) No reliance on reproductively established families e.g., spontaneously generated organisms (like mice from dirt, which are accidentally generated from the potentiality of matter; AT 3: 460). Ancient selectionist accounts rely on a principle of fitness not selection over generations. (ii) Selection presupposes function. (iii) Insufficient textual evidence of this in Descartes. Selectionism could be extended to include the recent history of an organism relying upon a principle of fitness. (Godfrey-Smith 1993; Griffiths 1993) But too weak to ground a notion of function because it would entail that anything which enhances the fitness of an organism would have a function for the organism. The boundary problem : Des Chene (2001, 132): Descartes never asks himself why the sun whose light acts on the eye is not part of the visual system. 2.5.Causal Functional Analysis Cummins (1975): A function is defined by reference to the causal contribution a part makes to a system s exhibiting some complex capacity. A causal analysis identifies a series of hierarchically organised subsystems with their own distinctive activity, the integrated activity of which accounts for the distinctive capacities of the whole. Analysing capacities must be less complex and different in kind from the capacities of the whole system, and for this reason not just any effect (e.g., the heart s making a thumping sound) will count as a function. A causal account fits with (1) Descartes denial of final causes, (2) his thoroughgoing mechanical explanation of biological systems, (3) his indifference to the reproductive history of systems, & (4) his denial of normativity in nature (AT 7: 84-5).

4 Example: Descartes Traité de l Homme is a paradigm example of the analytic strategy in operation. He begins by excluding the relationship between the human body and the soul. Such a being would have within it all the parts required to make it walk, eat, respire, and finally all of our functions which can be imagined to proceed from matter and to depend only on the disposition of the organs. [AT 11: 120] We are then asked to conceive of this body as having the bones, nerves, muscles, veins, arteries, stomach, liver, spleen, heart, brain and various other parts from which it must be composed and then to consider the parts which are too small to be seen about which we can learn enough if we know the movements which depend on them. [AT 11: 120 1] Employing this strategy Descartes concludes: I need only explain these movements in order [and] tell you by the same method which of our functions they represent. [AT 11: 121] 2.6. Problems: (1) Doesn t solve the boundary problem. (2) Doesn t distinguish between functions and fortuitous effects. (3) If functional analysis is merely a stepping stone on the path to a wholly reductive analysis what confidence do we have that functions are real? 2.7. Modified Causal/Cartesian Functional Analysis (1) allows that functions are real and mind-independent (2) is consistent with Descartes rejection of final and formal causes (3) distinguishes between functions and fortuitous effects, and (4) provides some relief to the boundary problem. Principle of Reciprocal Dependence: A part of matter, x, has a (proper, non-derivative) function, F, for producing effect, e, if x stands in hierarchically ordered relations of reciprocal dependence with other parts of matter for the performance of effects, g i g n, the combined effects of which explain the existence or persistence of each part and the complex capacities of the whole. Descartes account of embryogenesis: In embryogenesis the movement of the heart and arteries is the first and most general movement that we observe in animals. [AT 6:46; also AT 11: ] The process begins with a mixing of male and female seminal fluid; the denser parts eventually compact into flesh and bones; its more rarefied parts become the blood and animal spirits. [AT 11: ] The formation of the heart is the first stage and that by means of which other subsystems and viscera develop. Particles entering the heart are heated, rarefied, agitated and, as they expand, move according to the first law of motion in a straight line along the path of least resistance. [AT 11: 254; 318; 516; 599] Meeting with the resistance of the heart, particles of blood are forced into new areas compacting into new organs, beginning with the brain stem. [AT 11: 254] The repeated influx of particles, their expansion and expulsion accounts for the beating of the pulse. Upon meeting the resistance of the brain stem, the blood is forced back towards the heart, but encountering new blood from the heart is forced outwards and downwards, which leads to the formation of the spine and genital organs, on the one side, and the vena cava, the route back to the heart through the chest, on the other. [AT 6:134 6] At some point in its development, the foetus must start to produce something that acts like the ovum membrane in resisting external matter. This requires the formation of skin. [AT 11:274 6] Once a closed system is formed, the parts of an organism can only be nourished through replacement of matter until, finally, its parts become too hardened to receive new matter and the organism eventually dies. [AT 11: 596 7] 2.8. Advantages: (1) Functions attributed to the operations of reciprocally dependent structures do not depend on suppositions about God s intentions, final or formal causes. (2) The boundaries of a system can be curtailed by mutually dependent substructures. A system may include more than what we might think of as the organism e.g., a spider and its web.

5 (3) Extended phenotypic traits can be excluded as lacking reciprocal dependence, even if there is a relation of non-reciprocal dependency. (4) No normativity implied Limitations: (1) Cannot be extended to artefacts. (2) Does not account for all parts. (3) Reproduction not a function. (4) Where a part has multiple functions, it will fail to meet the condition of depending for its existence on its contribution to the success of any one other part performing its function. (5) Without normativity can we define health? (6) Is the identification of a system still arbitrary? PART 2 3. The Status of Organisms. Human bodies have a special status by virtue of their relationship to a soul: This is confirmed by the example of the soul, which is the true substantial form of man. For the soul is thought to be immediately created by God for no other reason than that it is a substance. Hence since the other forms are not thought to be created in this way, but merely to emerge from the potentiality of matter, they should not be regarded as substances. (Draft of letter from Regius to Voetius, written by Descartes; AT 3, 505; CSMK 208) Animals do not. However: (i) Animals have a special status as natural automata, self-moving machines. (AT 11: 120; Discourse V: AT 6: 55-6; To More: AT V: 277) (ii) Animals have a unity of composition (6 th Replies; AT 7: 423-4) (which I have argued is a functional unity). (iii) Animal and human bodies have the same organs and arrangement of parts. (AT 11: 200) (iv) Animals have life (their soul must be a part of the body not a mode i.e., the blood (AT 4: 64-5) or blood and spirits (AT 11: 202). (v) Animals have the first grade of sensation (AT 4:576; 5:276) (vi) Animals have a corporeal soul which depends solely on the force of the spirits and structure of our organs. (To More, 5 February, 1649; AT 5: 276). There is absolutely no principle of movement in animals apart from the disposition (arrangement) of their organs and the continual flow of spirits which are produced by the heat of the heart as it rarefies the blood. (AT 7:230) But what metaphysical status, if any, does this give to organisms? 3.1. Automata In his Two Treatises, Digby distinguishes between two types of compound body. Instances of the first kind have the same nature throughout and to this category he assigns plants. The organisation of a plant is characterised by one constant motion viz., the passage of moisture and nutrients up through the tubes of the plant (Ibid, 258) which varies only in diverse situations according to the disposition of the subject. (Ibid, 254-5) These are not automata. But of the second kind of compound body, he writes: [T]here are other bodies in which this manifest and notable difference of parts, carrieth with it such a subordination of one of them unto another, as we cannot doubt

6 that nature made such engines (if so I may call them) by design; and intended that this variety should be in one thing; whose unity and being what it is, should depend on the harmony of the several differing parts, and should be destroyed by their separation. As we see in living creatures, whose particular parts and members being once severed, there is no longer a living creature to be found among them. (Digby 1658, 255) (I) Heterogeneity of parts and motions, (II) Hierarchical organisation and interdependence of parts and functions, (III) Indivisibility (without loss of identity). (IV) Emergence. Cf: Descartes on I and II. The Description reverse engineers the human body, starting with the general notion of the entire machine and proceeding to analyze it in hydraulic terms as a system of interconnected parts connected by pipes (although the brain as we ve long suspected is more like a sieve). III & IV go together: where the whole has irreducible properties it is not divisible without loss of identity Organic natures Animals have natures : even if they are not transparently clear to us. (AT 7:117-8) If an automaton acted in ways indiscernible from an animal, they would be of the same nature. (AT 6: 56) This would make no sense if nature here had the same meaning as nature in the Sixth Replies discussion of unity, which is reserved for the essence of a substance, for no one would find it contentious that an artefactual automaton was, like an animal, composed of extension. Elsewhere Descartes is apt to use nature to refer to certain kinds of composites which are not substances. Some things have irreducible natures even though they are not technically substances but rather composed of them. One category of irreducible composite natures is included in that of true and immutable natures. Here we see Descartes relying on a criterion of emergence to settle when from composition a new nature is formed. The natures of simple substances do not change when aggregated unless their arrangement generates properties that cannot be accounted for in terms of the properties of the parts. If new properties are generated, then we must suppose the nature of the composite is different Animals and Objective Perfection Animals are natural automata. Automata of all kinds have what Descartes calls objective perfection (perfectio objectiva). [Principles I., 17 AT. VIII 11]. What this appears to mean for Descartes is that the more complex a machine, the more reality is present in our idea of the thing, and the more sophisticated must be its cause. If this is so then an automaton, and especially a highly intricate automaton like an animal, has more objective reality than does the bare matter of which it is constituted. Thus, while an animal is nothing other than bits of matter suitably arranged, the arrangement is not reducible to the properties of the component material bits. This is the analogue for animals of being united to the same mind. 4. Artificial Life The difference between a living and lifeless thing is thus simply like the difference between a clock or other automaton, and a key, sword or other instrument, which does not move of its own accord. (AT 3:566; CSMK 214, trans.alt.) I do not recognise any difference between artefacts and natural bodies except that the operations of artefacts are for the most part performed by mechanisms which are large

7 enough to be easily perceivable by the senses as indeed must be the case if they are to be capable of being manufactured by human beings. The effects produced in nature, by contrast, almost always depend on structures which are so minute that they completely elude our senses. (AT 8A: 326;CSM1: 288) 4.1. Criterion I: The Imitation Test (too weak?) I have been here [in the Traité de l Homme] particularly determined to show that if there were such machines [automata] that had the organs and figure of a monkey, or of some other animal without reason, we would not have any means of knowing that they were not wholly of the same nature as these animals. (Discourse, AT 6: 56) This suggests that Descartes would not have trouble with the idea of creating an artificial life and elsewhere he suggests the possibility of creating an artificial bird. (AT 3: 163) Descartes proposes inventing a human automaton using magnets. (AT 10: 231-2) Criterion II: Internal heat (source of motion) (too weak?) Criterion III: Blood (to Buitendijck, 1643(?)). (Too strong?) I do not remember ever having written that motion is the soul of animals; indeed I have not publicly revealed my views on the topic. But because, by the word soul, we usually mean a substance, and because I think motion is a mode of bodies, I would not wish to say that motion is the soul of animals I would prefer to say with the Holy Scripture (Deuteronomy 12.23) that blood is their soul, for blood is a fluid body in very rapid motion, and its more rarefied parts are called spirits. It is these which move the whole mechanism of the body as they flow continuously from the arteries through the brain into the nerves and muscles. (AT 4:64-5) 4.2. Solutions? (1) Heat wins because it accounts for self-motion, which in animals is the blood and in plants is something else. See To Mersenne, 30 July 1640 (AT 3: 122): As heat is a common principle for animals, plants and other bodies, it is no wonder that the same serves to make alive a human and a plant. (2) Relativise life to a specific set of life functions (MacKenzie, 1975) (3) Accept that life is not restricted to natural automata. 5. Artificial Intelligence? Against animal feeling and intelligence, Descartes writes: Yet suppose that we were equally used to seeing automatons which perfectly imitated every one of our actions that it is possible for automatons to imitate; suppose, further, that in spite of this we never took them for anything more than automatons; in this case we should be in no doubt that all the animals which lack reason were automatons too. For we would find that they were different from us in all the same respects [and] In my World I explained in great detail how the bodies of animals contain all the organs which an automaton needs if it is to imitate those of our actions which are common to us and the beasts. (To Mersenne, July 30, 1640; AT 3: 121; CSMK: 149) It seems conformable to reason that since art imitates nature and humans are capable of fabricating various automata in which there is motion without any cogitation, so too nature should produce her own automata, far more perfect than those by art, namely, all the brutes. (To More, Feb 5, 1649; AT 5: 277). 5.1Two Tests: Gunderson (1964) Action test: To demonstrate intelligence a thing has to be able to act in all the contingencies of life in the way that reason makes us act.

8 For whereas reason is a universal instrument which can be used in all kinds of situations, these organs [of animals] need some particular disposition for each particular action; hence it is morally impossible for a machine to have enough different organs to make it act in all the contingencies of life in the way in which our reason makes us act. (AT 6: 57) Problem: When Descartes isn t trying to establish a radical difference between human and animal behaviour he is apt to recognise: (a) that not all animal behaviours are hardwired (they are capable of learnt and adaptive behaviours; e.g., AT 5: 278; AT 1: 134; AT 11: ), and (b) that animal brains and nervous systems exhibit the kind of plasticity that accounts for our flexible behaviour. [AT 7: 229; CSM 2: 161] The Language Test 1. Compositionality it is not conceivable that such a machine should produce different arrangements of words so as to give an appropriately meaningful answer to whatever is said in its presence. (AT 6: 57) 2. Meaning The vocal sounds of magpies and parrots mimic the variety of our own but they do not refer to anything, produce any understanding or show that these animals are thinking what they are saying. (AT 6: 56-57; cf. also letter to Newcastle, Nov 23, 1646; AT 4: 574) 5.2. Response 1: if language production is algorithmic, that is, consists entirely of computable functions, then a Universal Turing Machine ought in principle be able to simulate it. (the Church-Turing thesis) Descartes imagines building a machine such that if you were to touch it in one spot, it would ask what you want, and if in another, cry out that you are hurting it, but none of this would convince us that the machine really has feelings. (AT 7: 56) Response 2: Do animal signals lack intrinsic intentionality? There is good evidence that animals are not merely producers of signs but consumers as well, and Descartes had ample opportunity in thinking about the role of information in a bodymachine having to navigate complex environments to consider this possibility. Princess Elisabeth: For if (the soul s moving the body) occurred through information, it would have to be that the spirits, which perform the movement, were intelligent, which you accord to nothing corporeal. (AT 3: 685; Shapiro (2007: 68) trans.; my emphasis) L Homme, Descartes uses the terminology of ideas to express how this information is processed in the brain so as to imitate perfectly the movements of a real human. (CSM 1:108; AT 11: 202) Similarly, in the Optics, visual perception involves a kind of unconscious reasoning. (AT 6: 137-8) 5.3. Does representation entail objective reality? (1) Third Meditation: a weaker notion of representation viz., indicating and referring. (AT 8A: 42; AT 7: 84-5; AT 11: ) (2) Can things exist objectively in extended substances e.g., Apelles painting. (AT 3: 567; CSMK: 214; To Regius, June 1642) 5.4. Animal Consciousness? To Plempius (Letter for Fromondus, October 3, 1637) animals do not see as we do when we are aware, but only as we see when distracted. In such a case the images of external objects are depicted on our retinas, and perhaps the impressions they make in the optic nerves cause our limbs to move, although we are quite unaware of them. In such a case we too move just like automatons, and nobody thinks that the force of heat is insufficient to cause their movements. (CSMK: 62; AT 1: )