Aristotle Critiquing Descartes' "Doubting of the Senses" 2000 Years Before He Argued It - Excerpt from Aristotle’s "Metaphysics" - Book IV - Chapters V and VI

"There is nothing new under the sun." I have no idea who this quote belongs to, but it is true in so many ways regarding philosophy. We attribute many ideas in Modern Philosophy to certain individuals ... but when one knows the Ancient Greek thinkers well, they begin to realize that the breadth and depth of Greek thought touched on almost everything that is later discussed, in some way. 

Here is a passage from Aristotle's Metaphysics Book IV chs. V and VI which deals with skeptics who doubt the objectivity of reality because of the nature of sense perception. His set up of the question and his response are to reminiscent of Descartes' Meditations on First Philosophy (i.e. Metaphysics) that one must assume that Descartes was influenced by it somehow. Even some of the phrases and examples that Aristotle uses such as not telling the difference between being asleep or waking ... makes Descartes' very original meditations seem less original. 

Appearance Versus Sensation

Aristotle begins this section by referencing his opponents who argue that truth is relative because things appear different to different people, such as weight to the strong person or the weak person, size to the person close up or far away, etc. [He even references the difference between "sleeping or to the waking", which is ironic given Descartes' Meditations.] Aristotle makes a distinction, though, between "appearance" and "sensation".

Sensation, he seems to use in the objective sense, as a perceiving of reality with an objective substrate. Appearance is the subjective person's experience of reality in this particular way or circumstance (not at a totality).

"Regarding the nature of truth, we must maintain that not everything which appears is true; firstly, because even if sensation-at least of the object peculiar to the sense in question-is not false, still appearance is not the same as sensation.-Again, it is fair to express surprise at our opponents' raising the question whether magnitudes are as great, and colours are of such a nature, as they appear to people at a distance, or as they appear to those close at hand, and whether they are such as they appear to the healthy or to the sick, and whether those things are heavy which appear so to the weak or those which appear so to the strong, and those things true which appear to the sleeping or to the waking.

No One Acts Like a Skeptic

No one acts as though the senses are completely relative. You would be a complete madman if you did. This is not some open question that really confuses people in their daily lives. The multiplicity of the senses are their unique grasp of reality provides a way by which to check and verify what is real if one of them is confused.

Even so, the senses uphold the PNC. They do not contradict themselves at the same time and in the same respect. Indeed, the senses receive what they receive from the world, the disagreement may come in regarding the judgment which attributes what is experienced the proper substance.

"For obviously they do not think these to be open questions; no one, at least, if when he is in Libya he has fancied one night that he is in Athens, starts for the concert hall.-And again with regard to the future, as Plato says, surely the opinion of the physician and that of the ignorant man are not equally weighty, for instance, on the question whether a man will get well or not.-And again, among sensations themselves the sensation of a foreign object and that of the appropriate object, or that of a kindred object and that of the object of the sense in question, are not equally authoritative, but in the case of colour sight, not taste, has the authority, and in the case of flavour taste, not sight; each of which senses never says at the same time of the same object that it simultaneously is 'so and not so'.-But not even at different times does one sense disagree about the quality, but only about that to which the quality belongs. I mean, for instance, that the same wine might seem, if either it or one's body changed, at one time sweet and at another time not sweet; but at least the sweet, such as it is when it exists, has never yet changed, but one is always right about it, and that which is to be sweet is of necessity of such and such a nature."

Skepticism Attacks the Underlying Substrata of Being

This relativism is really a metaphysical attack because if all is relative sense perception ... well what is being sensed? What is the the thing which provides the sensation? Who is the perceiver? The act of experiencing a sensation requires a deeper causal substructure of thing and perceiver before an experience can be generated.

"Yet all these views destroy this necessity, leaving nothing to be of necessity, as they leave no essence of anything; for the necessary cannot be in this way and also in that, so that if anything is of necessity, it will not be 'both so and not so'. "And, in general, if only the sensible exists, there would be nothing if animate things were not; for there would be no faculty of sense. Now the view that neither the sensible qualities nor the sensations would exist is doubtless true (for they are affections of the perceiver), but that the substrata which cause the sensation should not exist even apart from sensation is impossible. For sensation is surely not the sensation of itself, but there is something beyond the sensation, which must be prior to the sensation; for that which moves is prior in nature to that which is moved, and if they are correlative terms, this is no less the case."

Infinite Regress of Syllogistic Demonstrations

Those who bring up these questions and argue regarding what is to be called "objective" or normal, Aristotle says, are like "... puzzling over the question whether we are now asleep or awake." He says that these people are ultimately looking for the starting-point of all knowledge, and think that the starting point should be some type of syllogistic demonstration that one knows at all, so that one can then begin knowing. But there is not such syllogistic starting point. The starting point of demonstration cannot be demonstration, or you'd have an infinite regress of demonstrations. Rather, it must be a non-syllogistic starting point for syllogistic reasoning. There must be some self-existent substrate.

"Chapter 6 There are, both among those who have these convictions and among those who merely profess these views, some who raise a difficulty by asking, who is to be the judge of the healthy man, and in general who is likely to judge rightly on each class of questions. But such inquiries are like puzzling over the question whether we are now asleep or awake. And all such questions have the same meaning. These people demand that a reason shall be given for everything; for they seek a starting-point, and they seek to get this by demonstration, while it is obvious from their actions that they have no conviction. But their mistake is what we have stated it to be; they seek a reason for things for which no reason can be given; for the starting-point of demonstration is not demonstration. "These, then, might be easily persuaded of this truth, for it is not difficult to grasp; but those who seek merely compulsion in argument seek what is impossible; for they demand to be allowed to contradict themselves-a claim which contradicts itself from the very first.-But if not all things are relative, but some are self-existent, not everything that appears will be true; for that which appears is apparent to some one; so that he who says all things that appear are true, makes all things relative."

Turns Into Cartesian Subjectivism

And so these skeptics who wanted the "irresistible argument" [ironic Cartesian phrase #2] end up resorting to saying that truth is relative to the individual and their unique sense perceptions of things. And if everything is relative to someone's subjectivity, then it is the person's subjectivity which is the substrata for the being of things. Thus we end up "... so that nothing has come to be or will be without some one's first thinking so." [ironic Cartesian phrase #3]. This view makes the subjective experience primary over the objective reality of the world.

Aristotle then points out that being and thought are correlative to one another. (see chapter of The Categories for more on this). That means that in an objective world, for example, "the double" is correlative to "the half," not to something else like "the equal," that wouldn't make sense. So the correlatives of "man the thinker" to "that which is thought," likewise will be undermined in a non-objective world. What is left then? All that will be left is man as an idea of some unknown thinking thing. Thus all reality is also just relative to the whatever the "thinking thing" is. [I hope I am interpreting this section correctly. I haven't had the time to analyze the Greek yet, but this is what I am gathering from this translation.]

"And, therefore, those who ask for an irresistible argument, and at the same time demand to be called to account for their views, must guard themselves by saying that the truth is not that what appears exists, but that what appears exists for him to whom it appears, and when, and to the sense to which, and under the conditions under which it appears. And if they give an account of their view, but do not give it in this way, they will soon find themselves contradicting themselves. For it is possible that the same thing may appear to be honey to the sight, but not to the taste, and that, since we have two eyes, things may not appear the same to each, if their sight is unlike. For to those who for the reasons named some time ago say that what appears is true, and therefore that all things are alike false and true, for things do not appear either the same to all men or always the same to the same man, but often have contrary appearances at the same time (for touch says there are two objects when we cross our fingers, while sight says there is one)-to these we shall say 'yes, but not to the same sense and in the same part of it and under the same conditions and at the same time', so that what appears will be with these qualifications true. But perhaps for this reason those who argue thus not because they feel a difficulty but for the sake of argument, should say that this is not true, but true for this man. And as has been said before, they must make everything relative-relative to opinion and perception, so that nothing either has come to be or will be without some one's first thinking so. But if things have come to be or will be, evidently not all things will be relative to opinion.-Again, if a thing is one, it is in relation to one thing or to a definite number of things; and if the same thing is both half and equal, it is not to the double that the equal is correlative. If, then, in relation to that which thinks, man and that which is thought are the same, man will not be that which thinks, but only that which is thought. And if each thing is to be relative to that which thinks, that which thinks will be relative to an infinity of specifically different things."

PNC Always Remains Upheld

He concludes chapter six by saying that the Principle of Non Contradiction is the fundamental truth of reality, the consequences that follow from denying this [again, you can see how similar the skeptics of his time were to where Descartes ends up by denying the PNC in regard to the senses], and why people might try to hold this position.

"Let this, then, suffice to show (1) that the most indisputable of all beliefs is that contradictory statements are not at the same time true, and (2) what consequences follow from the assertion that they are, and (3) why people do assert this. Now since it is impossible that contradictories should be at the same time true of the same thing, obviously contraries also cannot belong at the same time to the same thing. For of contraries, one is a privation no less than it is a contrary-and a privation of the essential nature; and privation is the denial of a predicate to a determinate genus. If, then, it is impossible to affirm and deny truly at the same time, it is also impossible that contraries should belong to a subject at the same time, unless both belong to it in particular relations, or one in a particular relation and one without qualification."

My Notes on the Text

Ancient Greek Text