THE Philosopher ...

Descartes

In the later mediæval period, Aristotle was the philosopher.* His four-cause, act-potency metaphysic was that on which all major thinkers of the time erected their systems. For hundreds of years philosophers were Aristotelian as a matter of course. Their disagreements were intra-Aristotelian disagreements (which is not to trivialise them). And as contrary as, say, Aquinas and Occam were, they were both students of their master, Aristoteles. But from the early modern period onward, Descartes has mastered philosophy. He is for us the philosopher, not Aristotle. (And we're so Cartesian that, save by special training, we can't even read Aristotle without reading Descartes into him.) Descartes has set the terms of the debate, from mid-seventeenth century to present day. His qualia-quanta duoverse is that in which philosophers and scientists move. Our disagreements are intra-Cartesian disagreements. But whereas Peripateticism was explicit in mediæval philosophy, Cartesianism nowadays is almost always implicit. Today's neuroscientists, for example, are by and large Cartesian. Their logico-conceptual grammar is Descartes'. Etc. Yet they're generally unaware of this. Thirteenth-century academics in debate would quote Aristotle back and forth (as their auctor), but if neuroscientists speak the name of Descartes aloud, they don't do so with deference, for he's a superseded historical curiosity to them. Still, a crypto-Cartesian metaphysic is no less Cartesian for the prefix. E.A. Burtt is apposite here:

'The only way to avoid becoming a metaphysician is to say nothing ... Even the attempt to escape metaphysics is no sooner put in the form of a proposition than it is seen to involve highly significant metaphysical postulates ... What kind of metaphysics are you likely to cherish when you sturdily suppose yourself to be free from the abomination? Of course it goes without saying that in this case your metaphysics will be held uncritically because it is unconscious; moreover, it will be passed on to others far more readily than your other notions inasmuch as it will be propagated by insinuation rather than by direct argument. Now the history of mind reveals pretty clearly that the thinker who decries metaphysics will actually hold metaphysical notions ... He will share the ideas of his age on ultimate questions, so far as such ideas do not run counter to his interests or awaken his criticism. No one has yet appeared in human history, not even the most profoundly critical intellect, in whom no important idola theatri can be detected, but the metaphysician will at least be superior to his opponent in this respect, in that he will be constantly on his guard against the surreptitious entrance and unquestioned influence of such notions.' (The Metaphysical Foundations of Modern Science, pp. 227-229.)

To see just how radically dissimilar the Aristotelian and Cartesian metaphysics are, consider their philosophies of psychology. For an Aristotelian, body and soul as such are but abstractæ. They are matter (hyle) and form (morphe), withal potentia and actus, which in materio-formal composition are a single concrete substance (ousia). You are not your matter, not your material cause; and you are not your form, not your formal cause; you are informed matter, ensouled body. Peripatetics further spoke of vegetative, animal, and rational souls, which bespeak powers (dynameis). Rational, animal, and vegetable souls are so ordered that the former comprehend the latter, as a quadrangle comprehends a triangle and a straight line (Aristotle, De anima, II.3). Plants have only vegetative powers (e.g. nutrition and reproduction); brute animals have vegetative powers and sensitive powers moreover (e.g. appetition and locomotion); human animals have vegetative and sensitive powers and rational powers moreover (e.g. intellection and will). Thus, soul (psuchē) is a term for the defining powers (capacities, abilities, aptitudes) of a living thing.

For a Cartesian, body (now machine) and soul (now mind) are independent, mutually exclusive concretiones in causal interaction. The mind-machine distinction is not abstract and conceptual (as above) but concrete and actual. The mind is a res cogitans, a substance the essence of which is thinking; the machine is a res extensa, a substance the essence of which is extension. That which is bodily-mechanical (material, physical, natural) is that which is quantitative. That which is soulish-mental (immaterial, nonphysical, supernatural) is that which is qualitative. And as for you, human, you just are a mind within the qualiaverse, a mind that's contingently connected to a dysteleological machine within the quantaverse. There are neither vegetative souls nor sensitive souls; there are only rational souls (i.e. minds), the modes of which (e.g. percepts) are 'thoughts' in Descartes' idiolect (Principles of Philosophy, I.9). Thus, for Descartes, the proper and primary subject of experience is the mind (whereas for Aristotle it is the animate being in toto); it is the mind to which psychological concepts literally apply. And hereby experience is solipsistically privatized, inasmuch as other minds are not directly accessible.

Sherrington

The locus of mind-machine interaction for Descartes was the pineal gland situated between the hemispheres of the brain. For Thomas Willis (a few years later) the locus was the cortex, specifically the corpus callosum. And in this way the intra-Cartesian debate continued, mutatis mutandis, into the twentieth century. Previously we talked about Alan Turing and his Cartesius-dimidius premises. In Turing's time, the most formidable name in (what we now call) neuroscience was C.S. Sherrington (1857-1952), and Sherrington kept his Cartesianism intact.

'In all those types of organism in which the physical and the psychical coexist, each of the two achieves its aims only by reason of a contact utile between them. And this liaison can rank as the final and supreme integration completing its individual. But the problem of how the liaison is effected remains unsolved ... [Scientists] place the soul in the body and attach it to the body without trying in addition to determine the reason why, or the condition of the body under which such attachment is produced. This, however, seems to be the real question.' (The Integrative Action of the Nervous System, p. xxiii).

In other words, given the supposition that soul-body interaction happens, the real question is not so much where it happens but how, and no answers are ever forthcoming.† Sherrington himself conceded defeat: 'I would submit that we have to accept the correlation, and to view it as interaction ... The theoretically impossible happens' (Man on his Nature, p. 248). Note that for an Aristotelian (like Aquinas or Scotus) there is no soul-body interaction problem, no impossibility to overcome, for there is no soul-body interaction at all. Soul and body are both abstracted from a single unified substantia, and abstractions qua abstractions do not causally interact with each other. That would be a form of nonsense. But never mind. Onwards.

Eccles

John Eccles (1903-97), who studied under and later worked with Sherrington, kept his Cartesianism intact also. In what he called the 'dualist-interactionist hypothesis,' Eccles argued that the loci of interaction were in the pyramidal cells of the motor cortex (Human Mystery, p. 217). For Eccles' research had suggested to him that 'only a specialized zone of the cerebral hemispheres is in liaison with the self-conscious mind. The term liaison brain denotes all those areas of the cerebral cortex that potentially are capable of being in direct liaison with the self-conscious mind' (ibid., p. 358). Thus Eccles, too, presupposed that, did his utmost to answer where, and was silent as to how.

Penfield

Wilder Penfield (1891-1976), also a Sherrington protege, tried to be at least a methodological Cartesius dimidius, but it wouldn't last. 

'After years of striving to explain the mind on the basis of brain-action alone, I have come to the conclusion that it is simpler (and far easier to be logical) if one adopts the hypothesis that our being does consist of two fundamental elements ... It seems to me certain that it will always be quite impossible to explain the mind on the basis of neuronal action within the brain ... I am forced to choose the proposition that our being is to be explained on the basis of two fundamental elements' (The Mystery of the Mind: A Critical Study of Consciousness and the Human Brain, p. 80).

Aristotle could reasonably interject, 'What about my proposition?' But, excuse us, Descartes is our philosopher. And one may have any metaphysic one likes, so long as it's either whole-Cartesianism or half-Cartesianism retaining the dialectic of whole-Cartesianism. (Who could ask for anything more?) The latter super-folly is today's received wisdom. Penfield had rightly argued that a whole-Descartes is 'not so improbable' as a half-Descartes, for it would be absurd to say 'that the highest brain mechanism should itself understand, and reason, and direct voluntary action' (ibid., p. 82). Yet that was back in ye olden dayes of 1975. We have stronger stomachs for absurdity in 2017. But before moving ahead to contemporary neuroscientists, note that Sherrington, Eccles, and Penfield all followed Descartes in understanding mind and body to be independent substances that causally interact, and in understanding the mind to be the proper and primary subject of experience, to be that to which psychological concepts literally apply.

To be continued.

Footsies:

*‘There is a tenacious legend that the West learnt its Aristotle from the Arabic, but the fact is that the West turned to Arabic-Latin translations only in default of the more intelligible Greek-Latin ones.’ (Bernard G. Dod, ‘Aristoteles latinus’, in The Cambridge History of Later Mediæval Philosophy, p. 52.)

†And then there is the question of when—i.e. the very o'clock, to the minute-hand if not to the second-hand, at which the soul and the body are conjoined. Behold sixteenth-century medico Jean Fernel (whom Sherrington was enamoured of): 'Made at the beginning by the supreme creator of things, [the soul] migrates in a moment of time into the prepared and equipped body of the infant; this is held to happen in the fourth month, when heart and brain are already brought to completion' (Physiologia, VII.13). That this clock-watching question is a question at all is of course a choice reductio.