There is no movement apart from things; for change is always according to the categories of being; and there is nothing common to these and in no one category; but each of the categories belongs to all its subjects in either of two ways (e.g. 'thisness' for one kind of it is form, and the other is privation; and as regards quality one kind is white and the other black, and as regards quantity one kind is complete and the other incomplete, and as regards spatial movement one is upwards and the other downwards, or one thing is light and another heavy); so that there are as many kinds of movement and change as of being.