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.