"To localize an object means simply to represent the movements that would be necessary to reach it." These words of the great French mathematician and physicist Henri Poincaré offer a bold statement of an idea that goes back to George Berkeley: the experience of space is grounded, finally, in our sense of our bodies, in our sense of our own degrees of freedom of movement.
Berkeley thought that touch was the spatial sense, for it was the movement sense. Vision without touch would deliver only flat pictures of the world around us.
But what about touch without vision? Some thinkers, for example Marius von Senden, have challenged Berkeley's intuition, opposing it with observation that touch delivers not space, but time. After all, when you investigate an object with your hands you receive a series of sensations spread out in time. You never experience a manifold, that is, you never get objects and things as spread out, filling up the world, all at once. For that, you need sight.
Well, we can be pretty certain that the idea that you need sight to know space is misguided. After all, blind people clearly experience the world as spatially extended. The blind are not limited to a mere temporal series of sensations. (For a general discussion, see my Action in Perception.)
Less far-fetched than the idea that you need sight to experience the spatial structure of the world is the idea that you need sight in order to make pictures of such structure. Why? Well, because pictures, in the ordinary sense of the word, are constructions we make to show how things look, and the blind, however great their powers of perception may be, don't experience the looks of things.
John Kennedy, a cognitive scientist at the University of Toronto, has recently been working closely with a blind painter whose abilities would seem to call all this into question. Despite having been blind since birth — he has no eyes — he is able to make excellent pictures of real and imagined scenes. In particular, he is able to make pictures that accurately depict how the spatial structure of a scene would appear from a particular vantage point.
How does he do this?
As you watch the video below, keep these questions in mind. I'll return to them in a later post.
Could it be that you don't need to see to experience the world visually?
Or might it be that you don't need eyes and sensitivity to light in order to see?
Or perhaps it is possible to understand and so to make pictures of how things look without experiencing them visually?