Wednesday, September 2, 2015

3. Self-knowledge and neurophysiology – a reply to David Parker

David asked: ‘Why do you say that consciousness has to be non-corporeal?’

In my third answer I shall once again begin with Aristotle, this time contrasting the physical time of the Physics with the one-ness of time in the De Anima (On the Soul). In the Physics Aristotle defines time as the ‘before and after’ of movement in space, which can be measured and numbered.

In principle, this is how neurophysiology studies and depicts neural processes, relating them to time measured in milliseconds. Let me quote from Carpenter and Reddi’s Neurophysiology: ‘If we know the time-course of the permeabilities [of the nerve cell membrane] we should be able to calculate … the time-course of the action potential itself (p. 30-31) … If we try to stimulate a nerve with a pair of shocks, gradually reducing the interval of time between them … This period, during which it is impossible to stimulate the nerve for a second time, is known as the absolute refractory period (p. 33) … rapid depolarizations [of the nerve cell membrane] are more effective than slow ones, because they get at sodium as it were before potassium has time to rise … Sodium is quick on the draw, but quickly gives up and in fact keels over altogether because it gets inactivated … potassium rises slowly but inexorably to its final value (p. 34) … In nerves, information is mostly coded by the frequency of firing … temporal codes … when action potentials finally reach the end of the axon they open voltage-gated channels, which let calcium in. This then makes the terminal release the transmitter it contains from the vesicles in which it is normally stored. Since each spike is identical, it releases the same quantity of transmitter; consequently altering the frequency causes the rate of transmitter release to change, so that the original information is passed on to the target cell (p. 38-39) …

In the De Anima Aristotle notes that we discriminate between sensory perceptions of different sensory organs – when we consider a sugar cube, we are aware that its being sweet is different from its being white – and that this discrimination must be perceived by an agency that is one and undivided, in undivided time (hȏste achȏriston kai en achȏristȏi chronȏi, 426b22-29). Aristotle used the sweet and the white as examples, but he could have used the ‘before and after’, which he views as constitutive of our perception of time in the Physics, for from the point of view of the De Anima the past is perceived as different from the future in the undivided present.

The most remarkable aspect of Aristotle’s reflections on time in the Physics is the absence of the present: time is composed (sunkeitai) of the part that has been (to men oun autou gegone) and is not (kai ouk estin), and of the part that is going to be (to de mellei) and is not yet (kai oupȏ estin, 217b33-218a2). The ‘now’ (to nun) plays an important role in his deliberations about time, ‘but it is not a part of time’ (to de nun ou meros, 218a6); it demarcates time as the body that moves demarcates movement: “The ‘now’ follows the body carried along (tȏi de pheromenȏi akolouthei to nun), as time follows motion (hȏsper ho chronos têi kinêsei), for we gain knowledge of the ‘before and after’ in motion by means of the body carried along (tȏi gar pheromenȏi gnȏrizomen to proteron kai husteron en kinêsei), and the ‘now’ is (to nun estin) in so far as the ‘before and after’ is countable (hêi arithmêton to proteron kai husteron, 219b22-25).

Biochemical and bioelectrical processes studied by neurophysiology proceed in a space-time continuum outlined by Aristotle in his Physics.

In the De Anima Aristotle views the ‘now’ very differently: ‘For just as the one and the same says that the good and the bad is different (hoti heteron to agathon kai to kakon), so also when (hote) it says that the one is different and the other is different [must be one and undivided], the when is not accidental (ou kata sumbebêkos to hote)… the undivided one says thus (all’ houtȏ legei) both now and that now (kai nun kai hoti nun), together therefore (hama ara, 426b24-28).

The present comes into its own in Aristotle’s Rhetoric: ‘All that is pleasurable (panta ta hêdea) must be (anankê) either present in being actually perceived (ê en tȏi aisthanesthai einai paronta) or in being remembered as past (ê en tȏi memnêsthai gegenêmena) or in being hoped for as coming in future (ê en tȏi elpizein mellonta). For people perceive the present pleasures (aisthanontai men gar ta paronta), remember the past ones (memnêntai de ta gegenêmena), and hope for the pleasures to come (elpizousi de ta mellonta, 1370a32-35).’ The present is here reflected by Aristotle as the primary field of experience, the past and the future come into view in the present as memories or expectations.

The psycho-somatic effects of the interplay between the past, present and future can be studied on animals. Let me quote Carpenter and Reddi’s Neurophysiology: ‘Consider a classic example: Pavlov’s famous experiments with dogs … A dog is trained by frequent association of sound and food to salivate when a bell is rung. Since he didn’t do it before, there must have been a change in his neural connections … What we observe is that after sufficient pairings of food with bell, the bell alone eventually produces salivation … What it amounts to is fire together, wire together: neurons representing things that tend to happen together get physically linked together, so that brain eventually embodies a model of the outside world.’ (p.258)

In the ‘Self-knowledge as an imperative’ on my website I wrote: ‘Pace Carpenter and Reddi, in Pavlov’s experiments, as far as I can remember, the conditional stimulus preceded the unconditional stimulus; Pavlov engineered varied gaps between the two … The authors write that fire together, wire together “is the secret of cerebral cortex: it provides a mechanism for creating physical connections between neurons that are often active simultaneously.” But the neural mechanism of fire together, wire together cannot explain Pavlov’s experiments on dogs, let alone constitute a model of the outside world in the brain.’

I have looked at the Wikipedia entry on Pavlov’s experiments on dogs; there the conditioning I remembered from my reading Pavlov (some 57 years ago) is called trace conditioning. I remember most vividly Pavlov’s experiments with visual stimuli, which allowed him to observe the dog’s ability to discriminate between different figures flashed on a screen: A circle appears on the screen, a time interval, food. When the conditional reflex has been established, the circle is followed by no food, but an ellipsis on the screen is followed by food; the dog learns to differentiate between the two.

Pavlov’s experiments can be viewed in terms of the interplay between the past, present, and future. When the conditional reflex has been established, the present picture of a circle is perceived by the dog as an indication of the future, food is to come. When the circle ceases to be followed by food, it is followed by the discomfort caused by the digestive juices produced by the stomach; when it subsequently ceases to evoke any response, the past experience has affected the dog’s present.

Who owns a dog can make such experiments with a lot of fun. You throw your dog a ball. The dog runs to retrieve it. You pretend to throw the ball, the dog runs after it, but it remains in your hand.  After a few such futile attempts, the dog sits and watches you, its eyes full of expectation. If you go on disappointing it, it ceases to be interested, leaves you and does its own business.

The interplay between the present, past and future acquires a new level of intricacy and intensity thanks to our use of language. Consider a sentence from Kant’s Critique of Pure Reason, which I am borrowing from my last post devoted to Kant, ‘Ethical considerations concerning Kant’s transcendental ideality of space and time’, posted on August 27. In the post the sentence is abbreviated and translated by me; now I am bringing it in full in Meiklejohn’s translation: ‘Suppose now, on the other hand, that we have undertaken this criticism (Wenn aber die Kritik nicht geirrt hat,), and have learnt that an object may be taken in two senses, (da sie das Objekt in zweierlei Bedeutung nehmen lehrt), first, as a phenomenon (nämlich als Erscheinung,), secondly, as a thing in itself  (oder als Ding an sich selbst;); and that, according to the deduction of the conceptions of the understanding (wenn die Deduktion ihrer Verstandesbegriffe richtig ist), the principle of causality has reference only to things in the first sense. We then see how it does not involve any contradiction to assert, on the one hand, that the will, in the phenomenal sphere – in visible action, is necessarily obedient to the law of nature, and in so far, not free; and, on the other hand, that, as belonging to a thing in itself, it is not subject to that law, and, accordingly, is free. (mithin auch der Grundsatz der Kausalität nur auf Dinge im ersten Sinne genommen, nämlich sofern sie Gegenstände der Erfahrung sind, geht, eben dieselben aber nach der zweiten Bedeutung ihm nicht unterworfen sind, so wird eben derselbe Wille in der Erscheinung (den sichtbaren Handlungen) als dem Naturgesetze notwendig gemäss und sofern nicht frei, und doch andererseits, als einem Dinge an sich selbst angehörig, jenem nicht unterworfen, mithin als frei, gedacht, ohne dass hierbei ein Widerspruch vorgeht. B XXVII-XXVIII).

All this is one sentence in German; as you read it word by word, phrase by phrase, it sinks from the narrow straits of the conscious presence into the subconscious, yet in the subconscious it is all the time present, and in the interplay between the subconscious and the consciousness a nonverbal understanding of the sentence is growing, until it culminates when you reach the end of the sentence. If you then read Meiklejohn’s very free paraphrase, divided into two sentences, it may help you understand better the underlying German original, and Kant’s German may help you understand what Meiklejohn has done with it in his paraphrase. In doing all this, the time goes by, but your effort to understand Kant’s thought transcends the passing of time in the undivided presence (undivided into the Aristotelian ‘before and after’, the past and the future) of ever intensified understanding.

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