Commentary Aristotle Metaphysics
691. And those who say. He gives the sixth argument. He says that their position that all things are being moved is opposed to their first position—that contradictories are true of the same subject at the same time—because if something is and is not at the same time, it follows that all things are at rest rather than in motion. For nothing is being changed in terms of any attribute which already belongs to it (for example, what is already white is not being changed as regards whiteness).
But if it is possible for the same thing both to be and not be at the same time, all attributes will be present in all things, as has been proved above, because all will be one. Hence there will not be anything to which a thing can be changed.
Lecture 14
Truth does not consist in appearances
Now concerning the truth that not everything which appears is true, the following points must be taken into consideration. First, a sense is not false with regard to its proper object, but imagination is not the same as a sense.
Second, it is surprising if some should raise the question of whether magnitudes are as great and colors really such as they appear to those who are at a distance or to those who are close, and whether things are such as they appear to those who are healthy or to those who are ailing, and whether heavy things are such as they appear to those who are weak or to those who are strong, and whether those things are true as they appear to those who are asleep or to those who are awake.
For it is clear that they do not think so. Therefore, no one who is in Lybia, having dreamed that he was in Athens, would go to the Odeon.
Again, concerning future things, as Plato says, the opinion of a physician and that of a person who is ignorant of the art of medicine are not of equal value as to whether someone will get well or not.
Again, in the case of the senses, the perception of a foreign object and that of a proper object, or that of a kindred object and that of the object of the sense concerned, are not of equal value. In the case of colors it is sight and not taste which passes judgment; in the case of flavors it is taste and not sight which does this.
And no one of these senses ever affirms at the same time about the same subject that it is simultaneously both so and not so. Nor at another time does it experience any difficulty about a modification, but only about the object of which the modification is an accident. I mean, for example, that the same wine, either as a result of a change in itself or in the body, might seem at one time sweet and at another not. But sweetness, such as it is when it exists, has never changed; but one is always right about it, and sweetness itself is necessarily such as it is.
Yet all these theories destroy this, for just as things will have no substance, neither will they have any necessity, for that is necessary which cannot be in one way and in another. Hence, if anything is necessary, it will not be both so and not so.
And in general if only the sensible actually exists, there would be nothing if living things did not exist, for there would be no senses. Therefore, the position that neither sensible objects nor sensory perceptions would exist is perhaps true, for these are modifications of the one sensing.
But that the underlying subjects which cause perception should not exist apart from perception is impossible, for a perception is not the perception of itself, but there is some other thing besides the perception which must be prior to the perception. For that which causes motion is naturally prior to that which is moved, and this is no less true if they are correlative terms.
692. Here he begins to argue against the opinion that truth is equivalent to appearances; and in regard to this he does two things.
First, he rejects this opinion.
Second, he draws his intended conclusion, at let this suffice.
First, he argues dialectically against those who held this opinion because of some theory or difficulty.
Second, he argues against those who held this opinion because of insolence, at now there are some.
In regard to the first part he gives seven arguments.
The first of these is as follows. It has been shown that not all things are changeable, and concerning the truth that not everything which appears is true, these points must be considered. First, the proper cause of falsity is not the senses but the imagination, which is not the same as the senses. That is to say, the diversity of judgments made about sensible objects is not attributable to the senses, but to the imagination, in which errors are made about sensory perceptions because of some natural obstacle.
Now imagination is not the same as perception, as is proved in On the Soul 3, but is a motion produced as a result of actual sensing. Therefore, in attributing to the senses this diversity of judgments by which one person is considered to have a false perception of a particular object about which another has a true perception, they do not proceed as they should.
Another translation states this better, saying, first, it must be understood that a sense is not false with regard to its proper object, implying that no sense makes a mistake about its own proper object (for example, sight is not mistaken about colors). From this it is evident that the judgment which a sense makes about its proper sensible object is a definite one, so that there must be some definite truth in the world.
693. And if someone raises the objection that error sometimes arises even with regard to proper sensibles, his answer is that this is attributable not to the senses, but to the imagination; for when the imagination is subject to some sort of abnormality, it sometimes happens that the object apprehended by a sense enters the imagination in a way different from that in which it was apprehended by the sense. This is evident, for example, in the case of madmen, in whom the organ of imagination has been injured.
694. Second, it is. Then he gives his second argument, and it runs thus. It is surprising if some should raise the question, or be puzzled, as another text says, as to whether continuous quantities are such as they appear to those who are at a distance or to those who are close at hand. For it is just about self-evidently true that a sense judges quantities which are close at hand to be such as they are and those which are far away to be smaller than they are, because what seems farther away appears small, as is proved in the science of optics.
695. The same thing applies if someone raises the question of whether colors are such as they appear to those who are close at hand, for it is evident that the farther an agent’s power is extended when it acts, the more imperfect is its effect. Fire heats those things that are far away to a lesser degree than those which are close at hand. And for the same reason the color of a perfect sensible body does not change that part of the transparent medium which is far away from it as completely as it changes that part which is close to it. Hence the judgment of a sense is truer about sensible colors in things close at hand than it is about those in things far away.
696. The same thing is also true if someone asks whether things are such as they appear to those who are healthy or to those who are ailing, that is, to those who are ill. For healthy people have sensory organs which are well disposed, and therefore the forms of sensible things are received in them just as they are; and thus the judgment which healthy people make about sensible objects is true.
But the organs of sick people are not properly disposed, and therefore they are not changed as they should be by sensible objects. Hence their judgment about such objects is not a true one. This is clear with regard to the sense of taste; for when the organ of taste in sick people has been rendered inoperative as a result of the humors being destroyed, things that have a good taste seem tasteless to them.