If, then, 'that which is not' has several senses, and movement can attach neither to that which implies putting together or separating, nor to that which implies potentiality and is opposed to that which is without qualification (true, the not white or not good can be moved incidentally, for the not white might be a man; but that which is not a 'this' at all can in no way be moved), that which is not cannot be moved, and if this is so, generation cannot be movement; for that which is not is generated.