ces, and in some sense, no doubt, knowledge is to be
derived from them. But any statement as to what it is that our immediate
experiences make us know is very likely to be wrong. It seems to me that
I am now sitting in a chair, at a table of a certain shape, on which I
see sheets of paper with writing or print. By turning my head I see out
of the window buildings and clouds and the sun. I believe that the sun
is about ninety-three million miles from the earth; that it is a hot
globe many times bigger than the earth; that, owing to the earth's
rotation, it rises every morning, and will continue to do so for an
indefinite time in the future. I believe that, if any other normal
person comes into my room, he will see the same chairs and tables and
books and papers as I see, and that the table which I see is the same as
the table which I feel pressing against my arm. All this seems to be
so evident as to be hardly worth stating, except in answer to a man who
doubts whether I know anything. Yet all this may be reasonably doubted,
and all of it requires much careful discussion before we can be sure
that we have stated it in a form that is wholly true.

To make our difficulties plain, let us concentrate attention on the
table. To the eye it is oblong, brown and shiny, to the touch it is
smooth and cool and hard; when I tap it, it gives out a wooden sound.
Any one else who sees and feels and hears the table will agree with this
description, so that it might seem as if no difficulty would arise;
but as soon as we try to be more precise our troubles begin. Although
I believe that the table is 'really' of the same colour all over, the
parts that reflect the light look much brighter than the other parts,
and some parts look white because of reflected light. I know that, if
I move, the parts that reflect the light will be different, so that the
apparent distribution of colours on the table will change. It follows
that if several people are looking at the table at the same moment, no
two of them will see exactly the same distribution of colours, because
no two can see it from exactly the same point of view, and any change in
the point of view makes some change in the way the light is reflected.

For most practical purposes these differences are unimportant, but to
the painter they are all-important: the painter has to unlearn the habit
of thinking that things seem to have the colour which common sense says
they 'really' have, and to l