FACT

COMMON sense starts out with the assumption that what we know directly
is such things as trees, grass, anger, hope and so on, and that these
things have qualities such as solidity, greenness, unpleasantness and
so on, which are also facts directly known. It is not very difficult
to show that, if we examine the facts which we know directly, we
cannot find in them any such things as trees, grass, or minds, over
and above the various qualities which we say belong to them. I see one
colour and you see another: both of them are colours belonging to the
grass but neither of us can find anything among the facts known to him
corresponding to this grass, regarded as something over and above its
various qualities, to which those qualities are supposed to belong.

This drives common sense back unto its second line of defence where it
takes up the much stronger position of asserting that, while trees,
grass, minds, etc., are not among the facts directly known, their
qualities of solidity, greenness, etc., are. It is usual to add that
these qualities are signs of real trees, grass, etc., which exist
independently but are only known to us through their qualities.

It is much harder to attack this position, but its weakness is best
exposed by considering change as we know it directly, and comparing
this with change as represented in terms of qualities. Change, when
represented in terms of qualities, forms a series in which different
qualities are strung together one after the other by the aid of
temporal relations of before and after. The change perceived when we
look at the spectrum would thus have to be described in terms of a
series of colours, red before orange, orange before yellow, yellow
before green, and so on. We might certainly go into greater detail