HAMLET
My father!–methinks I see my father.

HORATIO
Where, my lord?

HAMLET
In my mind’s eye, Horatio.

From this we know that the ‘inward eye which is the bliss of solitude’ was a current notion in Shakespeare’s day, and doubtless it is a great deal older than that; yet a conversation I had today reminded me of something I struggled to put into words (rather badly) a long time ago.

I was writing, I recall, about David Hume, quite possibly in an exam, maybe in an essay. Hume, at that time, was a source of great annoyance to me: I found his logic unassailable, yet I was sure he was wrong. The consequence was that I rather foolishly picked fights with him at every turn, when all that the university authorities required was that I demonstrate an adequate familiarity with his work.

Anyway, what I was taking issue with on this occasion was Hume’s notion that

‘All the perceptions of the human mind resolve themselves into two distinct kinds, which I shall call IMPRESSIONS and IDEAS. The difference betwixt these consists in the force and liveliness with which they strike upon the mind, and make their way into our thought and consciousness. Those perceptions, which enter with most force and violence, we may name impressions…  By ideas I mean the faint images of these in thinking and reasoning’

(those of you familiar with Hume will recognise that as the opening sentences of his Treatise of Human Nature – I really didn’t get very far at all before I started objecting)

I remember conducting an experiment (and this makes me think it must have been an essay, though to be sure, I might have repeated the same argument in an exam): I stared at something – it was a brown le Creuset saucepan, in my recollection, but we’ll come back to that – and then I closed my eyes and attempted to attend to the ‘faint image’ of it in my mind.

I insisted at the time that there was nothing to be seen.

There was something – I could have drawn a picture from it, or described it  – a small, heavy cast-iron pan, brown on the outside, creamy off-white within, the handle tapered towards the pot, rounded at the end and pierced with a hole which gave access to the hollow interior. But an image? a picture?

It wasn’t like seeing, I insisted: my argument with Hume was that he said that ideas were faint copies of impressions – like seeing, only less vividly, more feebly – and I felt that was not the case.

(I remember rehearsing a similar argument with my late brother Brendan in a slightly different form – my case then was that we had learned to talk about dreams as if they were essentially visual, when in fact they weren’t – but we had drink taken and our faculties were impaired, not least by the fact we thought them enhanced)

When I think back on this now, I feel I was being hard on Hume, though I think I have a point worth considering. I can still call that saucepan to mind, but I am no no longer sure if it was indeed what I conducted my experiment with – my recollection is that it was, but in the intervening years I have grown less willing to rely on the accuracy of memory; I accept that it invents.

But what does this ‘calling to mind’ involve? Davy Hume did not have the advantage I have of being familiar with faded images – an old photograph, a photocopy made when the toner is running low – so it is easy for me to conjure such a thing and say that an ‘idea’ is not like that – for me, at any rate. And though it is hard on Hume, I think I was right in this respect – a faded photograph, a feeble photocopy emphasises the relation with the original – it is an inferior duplicate, the same kind of thing, but not so well-realised – and that is something that Hume wants to say, that ideas are mere copies of impressions, and the reception of them by the mind is entirely passive: impressions enter via our senses with ‘force and violence’ and leave an impression behind, as a seal upon wax (though Hume expressly repudiates the image implied in the word – another point on which I took issue with him – if he did not mean ‘to express the manner, in which our lively perceptions are produced in the soul’ then why not use some other word? he could have called them ‘humes’).

Schopenhauer explodes this view (building on Kant’s insight) by pointing out that perception is not mere passive reception, but an intellectual act – we do not receive impressions ready made, like postcards through a letter box; we create them by processing the data – it is more akin to taking a photograph (whether digitally or otherwise) – light is focused by a lens to produce a pattern on a receptive surface, and that pattern is then converted into a form that we can comprehend.

But back to our experiments. If I try to attend to what I ‘see’ when I call something to mind, I am not at all sure how to describe it. Two things strike me as noteworthy: there is always visual input alongside it, whether my eyes are open or shut (if they are shut, I have the dark inside of my eyelids, sometimes marked with afterimages of any bright light that was there when my eyes were open; if they are open, my ‘idea’ is not in any way superimposed on what I see – it does not exist in the same space – though attending to one distracts from the other); and I cannot hold it still – it seems always to ‘slip away’ just when I most want to ‘look’ at it (though equally I can ‘move around’ it:  it is not two- dimensional, and is more like a model than a picture). Yet in spite of these difficulties I can confidently produce verbal descriptions or drawings of what I am ‘calling to mind’ – and indeed using words to express what I have in mind strengthens and clarifies whatever it is.

It strikes me that the comparison I have made above may hold the answer: in digital photography, the image exists in another form which is clearly non-visual – it is digitized, binary code – yet it still corresponds exactly to the visual image, to which it can be converted at any time.  What I have been saying about ‘ideas’ above – that they have all the properties of a visual image (we can use them the same way, can convert them – by words or lines – into actual pictures) yet lack the obvious one – we can’t actually see them – has an exact parallel in digitized images stored on a card: our camera can read them, and convert them into a form that our eye can read; but with ideas, it is our brain (or mind) that ‘reads’ them.

In other words, we ‘store’ our ideas in a different form, but one we can comprehend directly (just as if we called something in French to mind, but gave the sense of it in English). The distinction can be made clearer if we consider an image cast by a lens: I remember as a child being delighted when our father showed us how to produce an image on the wall using a magnifying glass – there it was, exact in every detail, but miniature and inverted. The principles of the camera obscura have been known since antiquity, and it is not unlikely that Hume might have seen them demonstrated; enough was known about the physiology of the eye for him to form a notion of an image being exactly reproduced inside the head. What Hume (and my youthful self) lacked was a model of how that image might exist in a wholly different form yet remain readable.

So now I would like to say that all the data we draw on for our interior life – whether that is memory, dreams, imagining – is stored and read in a different form. It is only when we come to talk about it that we naturally fall into using the language of the senses: we speak, like Hamlet, of seeing in our mind’s eye, but it is a different kind of seeing.

And having arrived, with some labour, at the end of the journey I embarked on in that essay of thirty-odd years ago, I am unsure if it matters or not.