are in health have humors that are mixed with each other. For to 103 give to one kind of fluid a power to change objects, and not to another kind, is a fiction of the mind; for just as those who are in health are in a condition that is natural to those who are in health, and contrary to the nature of those who are not in health, so also those who are not in health, are in a condition contrary to the nature of those in health, but natural to those not in health, and we must therefore believe that they also are in some respect in a natural condition. Furthermore, 104 in sleep or in waking, the ideas are different, because we do not see things in the same way when we are awake as we do in sleep; neither do we see them in the same way in sleep as we do when awake, so that the existence or non-existence of these things is not absolute, but relative, that is in relation to a sleeping or waking condition. It is therefore probable that we see those things in sleep which in a waking condition do not exist, but they are not altogether non-existent, for they exist in sleep, just as those things which exist when we are awake, exist, although they do not exist in sleep. Furthermore, things 105 present themselves differently according to the age of life, for the same air seems cold to the aged, but temperate to those in their prime, and the same color appears dim to those who are old, and bright to those in their prime, and likewise the same tone seems faint to the former, and audible to the latter. People in different ages are also differently disposed 106 towards things to be chosen or avoided; children, for example, are very fond of balls and hoops, while those in their prime prefer other things, and the old still others, from which it follows that the ideas in regard to the same objects differ in different periods of life. Furthermore, things appear different 107 in a condition of motion and rest, since that which we see at rest when we are still, seems to move when we are sailing by it. There are also differences which depend on liking or 108 disliking, as some detest swine flesh exceedingly, but others eat it with pleasure. As Menander said-- "O how his face appears Since he became such a man! What a creature! Doing no injustice would make us also beautiful."