To: Foo W.
From: Geoffrey Klempner
Subject: Perception and the nature and limits of knowledge
Date: 30 November 2007 12:56

Dear Foo W.,

Thank you for your email of 24 November, with your fourth essay for Possible World Machine, in response to the question, 'What is perception? Explain the role of perception in an account of the nature and limits of human knowledge.'

The first question that your essay stimulates me to ask is, 'Is perception dispensable?' Those of us who are lucky enough to be able to see, hear, feel, taste smell can wonder what it is like to lack some -- or all? -- of these senses.

You described picking an object up to verify its reality, by turning it in your hands, feeling its texture. Consider a race of beings on another planet who grow from the ground, like trees. They have eyes and can wag their branches at one another in order to communicate, but are otherwise incapable of action. The trees have developed a complex social order. They have a state, an education system, a judiciary, etc. But the only 'crimes' that are ever committed are verbal ones. Their science is rudimentary as they are unable to perform experiments, but they are great mathematicians.

This thought experiment tests traditional accounts of perception, which prioritise sight as the main source of knowledge of the external world. We know, from history, that human beings are very credulous. Get a group of people together, and they can persuade one another that the earth is flat, or that they have seen a ghost or a UFO. Luckily, in the real world, reality has a way (eventually) of refuting false beliefs. But not so with our intelligent trees. Like human beings suffering from paranoid delusions, any belief that the intelligent trees hold can be 'verified by perception' since none of their beliefs have any practical consequences. How, in the case of the trees, does the truth prevail over error?

Indeed, is what I have just described, a real possibility? Have I described a 'possible world'? The fact that you can picture to yourself a tree with eyes, wagging its branches (like the 'Ents' in Lord of the Rings) doesn't prove that the description is logically coherent.

In the 20th century, the traditional 'passive observer' view of perception was attacked on a number of fronts: from phenomenology (Heidegger, Sartre, Merleau-Ponty), pragmatism (Pierce, Dewey, James) and in Britain by the work of John Macmurray and the later Wittgenstein.

Now contrast the opposite case, either the real life story of Mary Keller, who was born deaf, dumb and blind or eponymous hero of the Who's fictional rock opera 'Tommy'. If you are an agent, if you can move about the world, handle objects, make things, then the lack of other senses is not an insuperable barrier.

We can imagine a race of aliens born without the senses that we enjoy, who eventually develop science and technology and build artificial 'eyes' and 'ears' for themselves. (I remember seeing a feature on TV where a blind man was provided with a TV camera which stimulated a pad attached to his back with tiny pins which reproduced the camera image and enabled him to negotiate an obstacle course. A very painful way to see!)

As you argue, the fact that we are sometimes mistaken in what we think we see -- a straight stick immersed in water looks bent, or illusions of water on the road on a hot sunny day -- is not an argument for mistrusting perception. On the contrary, it is perception which tells us (on a closer look) that we have been misinformed.

Descartes makes this point in his First Meditation. He also considers the possibility that he may be dreaming. You argue that we would not know the difference between dreaming and being awake if we were not sometimes awake. Is that persuasive? Imagine someone who has spend their whole life in the Matrix. They have a concept of dreaming and being awake. Indeed, we can go further and suppose that in that persons' Matrix world there are cinemas showing a film called 'The Matrix'. In other words, it is not necessary to ever have been 'awake' (or not in the Matrix) in order to be able to form the concept of the distinction between non-waking and waking 'experience'.

It is a strange thing about human experience, that when we are exposed to extreme situations -- for example, some of your experiences in A+E departments, which I would prefer not to think about -- we tend to 'switch off' a part of ourselves, almost to the point of losing our sense of reality. You can almost imagine that you are watching a film, that this is not really happening. Perhaps this is a survival technique. If you can do what is necessary, perform your function effectively as a surgeon in just the same way as you would in a simulator -- without excessive emotion -- I imagine that the patient has a greater chance of survival.

All the best,

Geoffrey