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Society of Mind

24.4 default assumptions

When someone says, John threw a ball, you probably unconsciously assume a certain set of features and qualities of the ball, like color, size, and weight. These are your assumptions by default, the kind we talked about when we first introduced the idea of level-bands. Your assumptions about that ball might be derived from some ball you owned long ago — or, possibly, your newest one. It is our theory that such optional details are usually attached too weakly to hold against the sharp insistence of reality, so that other stimuli will find them easy to detach or otherwise adapt. This is why default assumptions make weak images, and why we aren't too amazed when they turn out wrong. It is no surprise that frames share so many properties of K-lines, since the terminals of frames themselves will lie in level-bands near the K-lines whose fringes represent our expectations and default assumptions.

But why use default assumptions at all, instead of simply seeing what's really there? Because unless we make assumptions, the world would simply make no sense. It would be as useless to perceive how things actually look as it would be to watch the random dots on untuned television screens. What really matters is being able to see what things look like. This is why our brains need special machinery for representing what we see in terms of distinct objects. The very idea of an object embodies making many assumptions that go without saying — for example, that it has substance and boundaries, that it existed before we saw it, and that it will remain afterward — in short, that it will act like other typical objects. Thus, though we never see every side of an object at once, we always assume that its unseen sides exist. I suspect that the larger part of what we know — or think we know — is represented by default assumptions, because there is so little that we know with perfect certainty.

We use default assumptions in personal relations, too. Why do so many people give such credence to astrology, to classify friends by the months of their births? Perhaps it seems a forward step, to class all persons into just twelve types — to those who once supposed that there were less. And how does the writer's craft evoke such lifelike characters? It's ridiculous to think that people could be well portrayed in so few words. Instead, our story writers use phrases that activate great networks of assumptions that already lie in the minds of their readers. It takes great skill to create those illusions — to activate unknown processes in unknown readers' minds and to shape them to one's purposes. Indeed, in doing so, a writer can make things clearer than reality. For although words are merely catalysts for starting mental processes, so, too, are real things: we can't sense what they really are, only what they remind us of. As Proust went on to say:

Each reader reads only what is already inside himself. A book is only a sort of optical instrument which the writer offers to let the reader discover in himself what he would not have found without the aid of the book.