understand, is not what we mean by _light_: we mean by _light_ just
that which a blind man can never understand, and which we can never
describe to him.

Now this something, which all of us who are not blind know, is not,
according to science, really to be found in the outer world: it is
something caused by the action of certain waves upon the eyes and
nerves and brain of the person who sees the light. When it is said
that light _is_ waves, what is really meant is that waves are the
physical cause of our sensations of light. But light itself, the
thing which seeing people experience and blind people do not, is not
supposed by science to form any part of the world that is independent
of us and our senses. And very similar remarks would apply to other
kinds of sensations.

It is not only colours and sounds and so on that are absent from the
scientific world of matter, but also _space_ as we get it through
sight or touch. It is essential to science that its matter should be
in _a_ space, but the space in which it is cannot be exactly the space
we see or feel. To begin with, space as we see it is not the same as
space as we get it by the sense of touch; it is only by experience in
infancy that we learn how to touch things we see, or how to get a
sight of things which we feel touching us. But the space of science
is neutral as between touch and sight; thus it cannot be either the
space of touch or the space of sight.

Again, different people see the same object as of different shapes,
according to their point of view. A circular coin, for example,
though we should always _judge_ it to be circular, will _look_ oval
unless we are straight in front of it. When we judge that it _is_