On July 30 David Parker replied to my ’Notes on the relevance of neurophysiology to self-knowledge’ (‘David Parker’s reply’, posted on July 30). In response, I wrote to him: ‘I am at present absorbed in Kant and Aristotle, but I should like to reply to your comments before I go to Prague for my 'Three days' in September. You write 'that what we know about the brain now is sufficient to offer, in principle, a physiological account of consciousness.' I shall contend that what we know about the brain now is sufficient for us to realize that what we experience thanks to our brains cannot be performed by our brains; there must be a non-corporeal entity that transforms what goes on in the brain into the world in which we live.’
David asked: ‘Why do you say that consciousness has to be non-corporeal?’
I answered: ‘Aristotle may help; he notes that topos (place/space) has three dimensions, length, breadth and depth, by which all body is defined. This might suggest that topos is a body, and so he says that the place cannot be body; for if it were, there would be two bodies in the same place (Physics, 209a6-7). He argues that two bodies cannot be at one and the same place (213b20).
Everything that neurophysiology has so far detected and can ever detect in the brain by the technology corresponds to Aristotle’s notion of body: where is neuron A, there cannot be neuron B, where is a vesicle A containing neurotransmitter ‘a’, there cannot be a vesicle B containing the same (or different) kind of neurotransmitter. The action potential generated at the axon hillock propagates as a wave along the axon …
When I look out of the window, I can see trees with their branches, a church and a few houses discernible behind the trees, Cam Peak in the distance, the blue sky-scape with the white clouds – all this is in space, all this is real. In so far as I see it, it all is composed in my brain on the basis of the neural structures inside the brain. Since what I can see in space around me – in my head – is real, in three dimensions, it cannot be corporeal, for in my brain there is no space for such corporeal structures.’ (‘A provisional reply to David Parker’, July 31)
David replied: ‘I accept that two bodies cannot be in the same place. But consciousness would not be considered as building a physical representation of the outside world by adding neurons or something else to locations in an already packed brain.’ (‘David Parker’s response’, August 5)
But this is just the point; as David says, ‘consciousness would not be considered as building a physical representation of the outside world by adding neurons or something else to locations in an already packed brain.’ The three dimensional space, which is there for him, in front of him and all around him – in his head – the moment he opens his eyes, composed as it is on the basis of the activities of neurons organised in neural networks inside his brain, cannot be physical, and yet it is there, in his head: it therefore must be non-corporeal.
David implies that our consciousness is building a non-physical representation of the outside world. Although I agree that what I can see in front of me is a non-physical representation of the outside world, I cannot agree that it is built by my consciousness, for what I can see in front of me is just there; the computer screen in front of my eyes, at which I am gazing as I am thinking what to write next; the keyboard on which I am typing …
Since I can see and perform all this only because I have my eyes open, because the electromagnetic waves reflected by the computer screen – by the keyboard, by the desk behind which I am sitting – impinge on the cones and rods in my retina, because the signals triggered by these are propagated into the visual centre in the brain – where these signals are connected with memory structures corresponding to lines and corners, and objects, and a computer screen and a keyboard, and with the networks corresponding to words I generate as I am thinking and re-thinking what I am going to type, networks that must be different from those that correspond to my checking and re-checking on the screen what I have written – all this must be connected with motor-cortex, which is guiding my hands and my fingers as I am typing …
Since the brain structures and brain activities involved in all this are completely different in space and in time from what I can see and what I am conscious of as performing in the space where I sit and in the time in which I do my thinking and typing, there must be a non-corporeal entity in my brain, which is intimately related to the brain structures and the brain activities involved in all this, the entity which is transforming those brain activities into that of which I am conscious as being in front of me and of which I am conscious as doing. Of this entity, which performs this transformation, I am entirely unconscious; it is the sub-consciousness, which makes my consciousness possible.
My sense organs and my brain, which are corporeal, my sub-consciousness and my consciousness, which are non-corporeal, are jointly engaged in a closely knit interplay thanks to which I can see what is in front of my eyes and do what I am doing.