Helgoland by Rovelli, Erica (ebook reader below 3000 .txt) 📗

less so. The fractures are just gaps in our understanding. This is the sense of the question about the physical basis of the notion of meaning earlier in this chapter.

The relational perspective distances us from subject/object and matter/spirit dualisms, and from the apparent irreducibility of the reality/thought or brain/consciousness dualism. If we come to untangle the processes that take place in our bodies and their relations with the external world, what is left to understand? What is the phenomenology of our consciousness if not the name that these processes assign to themselves in the game of mirrors of relevant information contained in the signals carried by our neurons?

There remains what Chalmers calls the “easy” problem, which is anything but easy and anything but solved. We understand little about the workings of the brain. But there is no reason to suspect that in our mental life there is something not comprehensible in terms of the known natural laws.

Objections to the possibility of understanding our mental life in terms of known natural laws, on closer inspection, come down to a generic repetition of “It seems implausible to me,” based on intuitions without supporting arguments.*131 Unless it is the sad hope of being constituted by some vaporous supernatural substance that remains alive after death: a prospect that, apart from being utterly implausible, strikes me as ghastly.

As the American philosopher Erik C. Banks writes, in the quotation with which this chapter began, “However mysterious the mind-body problem may be for us, we should always remember that it is a solved problem for nature. All we have to do is figure out that solution by naturalistic means.” Quantum theory does not give us a direct solution, but it changes the terms of the question.

VII

BUT IS IT REALLY POSSIBLE?

In which I try to conclude a story that has no conclusion.

You do look, my son, in a moved sort,

As if you were dismay’d. Be cheerful, sir.

Our revels now are ended. These our actors,

As I foretold you, were all spirits and

Are melted into air, into thin air.

And, like the baseless fabric of this vision,

The cloud-capp’d towers, the gorgeous palaces,

The solemn temples, the great globe itself,

Ye all which it inherit, shall dissolve.

And, like this insubstantial pageant faded,

Leave not a rack behind. We are such stuff

As dreams are made on, and our little life

Is rounded with a sleep.

One of the most fascinating recent developments in neuroscience concerns the functioning of our visual system. How do we see? How do we know that what we have in front of us is a book, or a cat?

It would seem natural to think that receptors detect the light that reaches the retinas of our eyes and transform it into signals that race to the interior of the brain, where groups of neurons elaborate the information in ever more complex ways, until they interpret it and identify the objects in question. Neurons recognize lines that separate colors, other neurons recognize shapes drawn by these lines, others again check these shapes against data stored in our memory. Others still arrive at the recognition: it’s a cat.

It turns out, however, that the brain does not work like this at all. It functions, in fact, in an opposite way. Many, if not most, of the signals do not travel from the eyes to the brain; they go the other way, from the brain to the eyes.132

What happens is that the brain expects to see something, on the basis of what it knows and has previously occurred. The brain elaborates an image of what it predicts the eyes should see. This information is conveyed from the brain to the eyes, through intermediate stages. If a discrepancy is revealed between what the brain expects and the light arriving into the eyes, only then do the neural circuits send signals toward the brain. So images from around us do not travel from the eyes to the brain—only news of discrepancies regarding what the brain expects do.

The discovery that sight functions in this way came as a surprise. But if we think about it, it becomes clear that this is the most efficient way of retrieving information from the surroundings. What would be the point of sending signals toward the brain that do nothing but confirm what it already knows? Information technology uses similar techniques to compress files of images: instead of putting into the memory the color of all the pixels, it stores information only on where the colors change. That is less information, but enough to reconstruct the images.

The implications for the relationship between what we see and the world, however, are remarkable. When we look around ourselves, we are not truly “observing”: we are instead dreaming an image of the world based on what we know (including bias and misconception) and unconsciously scrutinizing the world to reveal any discrepancies, which, if necessary, we will try to correct.

What I see, in other words, is not a reproduction of the external world. It is what I expect, corrected by what I can grasp. The relevant input is not that which confirms what we already know, but that which contradicts our expectations.

Sometimes it is a detail: the cat’s ear has moved. Sometimes something alerts us to jump to a new hypothesis: it isn’t a cat, it is a tiger! Sometimes it is a wholly new scenario, which we try to make sense of by imagining a version of it that would makes sense to us. It is in terms of what we already know that we seek to give sense to what arrives at our pupils.

This could even be a way in which the brain operates in general. In the model known as PCM (projective consciousness model), for example, the hypothesis is that consciousness is the activity of the brain constantly attempting to predict the input that constantly varies because of the variability of the world and the change of our position. Representations are techniques to minimize mistakes in predictions