These are the secondary qualities of matter.
Why should we perceive secondary qualities?
It seems an extremely unfortunate arrangement that we should perceive a lot of things that are not there.

Yet this is what the theory of secondary qualities in fact comes to.

There is now reigning in philosophy and in science an apathetic acquiescence in the conclusion that no coherent account can be given of nature as it is disclosed to us in sense-awareness, without dragging in its relations to mind.

The modern account of nature is not, as it should be, merely an account of what the mind knows of nature; but it is also confused with an account of what nature does to the mind.

The result has been disastrous both to science and to philosophy, but chiefly to philosophy.