4. Critical realism

5. Idealism

6. If idealism is true, we have no bodies!

7. The truths of arithmetic can be doubted

8. Solipsism; you are entirely alone

9. Skepticism and cause/effect judgements

10. Correspondence theory of truth and its difficulties

11. Problems with a coherence theory of truth

4. Sense data can give us some sort of knowledge of the way the world works; critical realism.

The position described by the yes answers is called mathematical or critical realism. A mathematical realist maintains that sense data do not represent the external world adequately, but may be used to give us indirect information from which we may be able to obtain mathematical descriptions which apply to the external world so that we may be able to predict and control it. We will never have a TRUE knowledge of the external world, but we can derive laws that apply to that world which laws can be checked out through sense data. These mathematical laws are the best possible descriptions we can have of the real world, but it is all important to note, that the laws themselves are not sensible --they cannot be sensed.

So far, where has our experiment gone? We are in the position held by the mathematical realist. We know we have sense data. The sense data are not adequate representations of the external world which causes our sense data. But, we can use sense data to obtain mathematical descriptions of the external world. We can use those descriptions to predict and control that world --to survive and improve our lives in it.

Well, so far, so good. But, Descartes now drops another bombshell on us. Consider the following.

5. Maybe nothing exists except minds; idealism.

"But it may be that although the senses sometimes deceive us concerning things which are hardly perceptible, or very far away, there are yet many others to be met with as to which we cannot reasonably have any doubt, although we recognize them by their means. For example, there is the fact that I am here, seated by the fire, attired is a dressing gown, having this paper in my hand and similar matters. And how could I deny that these hands and body were mine, were it not perhaps that I compare myself to certain persons whose cerebella are so troubled and clouded that...they are mad, and I should not be any the less insane were I to follow examples so extravagant." "At the same time I must remember that I am a man, and that consequently I am in the habit of sleeping, and in my dreams representing to myself the same things or sometimes even less probable things, than do those who are insane in their waking moments. How often has it happened to me that in the night I dreamt that I found myself in the particular place, that I was dressed and seated near the fire, whilst in reality I was lying undressed in bed! At this moment it does indeed seem to me that it is with eyes awake that I am looking at this paper; that this head which I move is not asleep, that it is deliberately and of set purpose that I extend my hand and perceive it; what happens in sleep does not appear so clear nor so distinct as does all this. But in thinking over this I remind myself that on many occasions I have in sleep been deceived by similar illusions, and in dwelling carefully on this reflection I see so manifestly that there are no certain indications by which we may clearly distinguish wakefulness from sleep that I an lost in astonishment. And my astonishment is such that it is almost capable of persuading me that I now dream."


(The movie Inception has its roots in Descartes' analysis. See the excursus on memes to get a quick overview of how a belief that the world is not real, but a construction of a active dream can confound one's mind.)

6. If idealism is true, then there is no material world and we have no bodies; our existence consists purely as thinking things.

Mathematical or critical realism has two components: 1, the world of external material objects somehow cause our sense data; and 2, sense data cannot represent adequately these external objects, but we can use sense-data to derive laws which will predict what kind of sense-data will follow others. At best, we can use mathematical language to describe the relationships among our ideas considered as causally related events. That is to say, by constructing experiments, we can abstract or apply mathematical descriptions to the ideas we have in our minds such that we can describe them mathematically and causally. For example, we might have a series of ideas in our minds about falling balls from a certain height and apply a formula to the data collected. The formula turns out to be the speed of falling objects given a gravitational force; it is 16gt2. So, if we were to have other ideas of falling objects and we knew the height from which they were dropped, we could predict from that formula where we would have the experience of the falling balls after a certain period of time.

Well, this is all well and good IF there is an external world. But, what if there is not? Descartes says that we can doubt that there is an external material world apart from our minds. Even worse, part of that external world is our bodies!

WHAT!!!? Such a suggestion by Descartes must be absurd. There is no question that we have bodies; I know I have one because I can feel it --I exist in it. Ridiculous, Descartes is out of his mind.

"Exactly," Descartes would reply. "I and all of you are out of your minds in the sense that you cannot know with certainty that your minds are IN your bodies, in fact, in any kind of material world." Let's take a close look at this notion.

Put yourself back into the video studio. How do you know that there is a car parked outside? Well, previously you would have the mobile cameras walk out and look at the street. On the screen, the image of a car appears and the statement, "There is a car parked on the street" is affirmed. But, what is really being affirmed is that a statement is being correlated to images on the screen such that it is said that it is confirmed that the statement about a car's being parked outside is true. Remember, we can never leave the TV studio and walk outside a door to check and see whether or not there REALLY is a car; all we have to go on are the images on the screen. Further, there are no remote cameras that we can be certain of; that is, there are no "supersensory" detectors to verify ordinary sense mechanisms. So, it is very much in doubt that there is a car out there. The sensory world and thus the world of objects, as far as we can determine, ends at the edge of our screens.

But, there is more. Now hold your arms out in front of you. You see your arms. But, what you see are images on your screen, no more and no less real than the image of the car. The notion that you have a body comes from the judgment that the images you have of it belong to you; that you have a body separate from those images which are representations of it. The important word here is "judgment." You infer that you have a body from the images on your screen just as you infer that there is a car parked outside. In both cases, the judgment could be wrong. How so? Well, you could be dreaming that there is a car and also that you have a body. People walk, fly, fall off mountains and so on with all the appropriate sensations involved in their dreams; they FEEL or SENSE that they have a body and do things with it. And don't try to con me that you haven't had a strange body in your dreams, something that could do things your "regular" body could not. So, which is the real body? The one you have when you are "awake" or the one when you are in a dream state? In terms of verification from sense data, both are equally real or unreal.

Just consider. How do you know for CERTAIN that at this very moment, you are not sound asleep having the dream that you are awake reading this material? It is possible, isn't it? And if it is, then the body that you have in this dream is a fiction. But, if that were true, then that is all Descartes needs to cast doubt on the truth of the proposition that we really do have bodies with all of their sensory organs. It could actually be the case that what we are minds only, and that our bodies are simply peculiar ideas which those minds have. Put another way, all that exists are minds with their ideas. That thesis, by the way, is called IDEALISM; it is the metaphysical doctrine that reality consists only of mental entities, minds.

7. Even the supposed truths of arithmetic can be doubted.

Wait a minute. Descartes thinks he is so smart, but let's outwit him. "Sure, Descartes," we could say, "It could be the case that everything material is suspect, because it is external to our minds. But, what about arithmetic? When I think 2+2=4, I am not sensing anything in the external world. Further, only an idiot would doubt that 2+2 equals anything other than 4. Moreover, even if there were no minds at all, it would still be true that 2+2=4. Arithmetic is not mind dependent. Arithmetic must be certain knowledge. It is not corrupted by sensation or anything bodily. Further, it seems to be internal to the mind, yet not mind dependent for its existence. Arithmetic is beyond doubting. Gottcha Descartes."

But, Descartes is not through and hits our thesis about arithmetic hard.

INSERT: "Nevertheless I have long had fixed in my mind the belief that an all-powerful God existed by whom I have been created such as I am. But how do I know that He has not brought it to pass that there is no earth, no heaven, no extended body, no magnitude, no place, and that nevertheless (I possess the perceptions of all these things and that) they seem to me to exist just exactly as I now see them? And, besides, as I sometimes imagine that others deceive themselves in the things which they think they know best, how do I know that I am not deceived every time that I add two and three, or count the sides of a square, or judge of things yet simpler, if anything simpler can be imagined?" (Descartes, Meditations on First Philosophy; Meditation II)

Suppose there is a powerful Evil Genius who fools us into thinking that 2+3=5 when in truth the answer is 4 or that the sides of a square total to four when in truth, they amount to six. It is possible to doubt the truth of arithmetic if there is this Genius. But, do we even need the Evil Genius to doubt the truths of arithmetic? Do this simple experiment. Add 1/3+1/3+1/3. The answer is 1. Now, add 1/2+1/2. The answer is also 1. Now do the same addition operationally. Start with the 1/2s. Divide 1 by 2 and the answer is .5. Add .5 and .5 to obtain the answer 1. Now divide 1 by 3. The answer is .333333. Add .333333 +.333333 +.333333 to obtain .999999. Whoops! Where did the 1 go? Try dividing a whole number by 0. Can't be done, even though you can multiply any number by 0 and get 0. Take the number 4. You can find the square roots of four (+2, -2; either of these numbers times itself will give four). But try finding the square root of -2. Now we get into something weird called "imaginary numbers." Something is wrong with the symmetry of arithmetic; the answers sometimes don't come out at the way they are supposed to come out given a desire for symmetry. So, it looks as though arithmetic is capable of being doubted with respect to its absolute certainty, for its answers do not always come out precise.

8. Solipsism. Why being alone in one's "video theater is so scary.

Where do we stand? To summarize, let's see where our experiment has left us. We have doubted that sense data can tell us anything about the external world, save some mathematical predictions about the predictability of sequences of our ideas. Then we doubted that there was an external world and that we had a body to even sense things in that external world. Finally, we doubted that arithmetic could give us truth, which casts into doubt the thesis that the mathematical descriptions of the external world are trustworthy. Right now, all that we can be sure of is that we have minds and that our ideas are in those minds. Our worlds consist of the ideas that we have in our minds, on our screens so to speak.

Let me slip in a little science-fiction to spice up things. What about those minds, our minds? How do they have the ideas they do given that we cannot be sure that the ideas are caused by an external world? What if all the ideas on our screens are caused by our own minds?

INSERT: WITH A FINGER IN MY I by David Gerrold (This story is available in Book #4 of The Road to Science Fiction, ed. by James Gunn, (New York: Mentor Books, 1982). Library of Congress Catalog Card Number is 78-070642.)

(Summary of the story: A person finds that the congruity of his ideas derives from other persons having similar beliefs. As these persons develop dissimilar beliefs, his and their perceptions of the world radically change. For example, if enough of us believed that clouds were made of cottage cheese, they would be perceived as being cottage cheese. The coherency of perceptions of the world falls apart as different minds have different fundamental beliefs with respect to what the world really is.)

Interesting story. Given that Descartes has left us only with our minds, what if the world on our screens is nothing more than the "majority world-view of all minds?" Whatever ideas we have about the world are the outcomes of majority agreement --the best hypothesis about the world. If we all believed the world to be flat, it would be flat. We now believe it to be round, so it is now round. World-views would be like choosing a language and culture. Communication would be in that language and whatever objects there are in the world would be the product of agreed upon concepts. If there were no word or concept of "square" in a chosen language, there would be no squares in our experiences, no squares on our screens. Thank goodness, that everyone in the world has pretty much the same beliefs. (Incidentally, a philosopher named Berkeley, an idealist, dealt with this problem by saying that God was the mastermind who held the "big picture" together.)

But, as the sci-fi story points out, what would happen if there were no God and no one agreed upon very many concepts at all. The world as it would appear to us would have no regularity or coherency and would literally fall apart as it did in the story. Each person's view would be entirely arbitrary and thus chaotic. There could be no knowledge, and very little communication. Everyone would become complete SKEPTICS; they would doubt whether there are any good reasons (evidence) to support any conception of reality or knowledge.

9. Skepticism does away with science or the ability of us to make cause-effect judgments.

Skepticism has two forms, weak and strong. The strong skeptic holds that there is no possibility for true knowledge at all; no proposition about the world has any truth value whatsoever. The weak version says that beliefs are at best only probably true, and that the best hypothesis can often turn out to be dead-wrong.

The strong version is a bit much; it puts us at the end of the sci-fi story in pure chaos. That's just not the case. The weak version is much more tenable.

A philosopher named David Hume was a proponent of the weak version. His thesis went something like this. All ideas about the world come to us through sensation or, as Descartes would have, ideas of the world gained through sensation are "adventitious" ideas --they come to us without our being entirely in very much control of what they will be and what they will be like. Our beliefs about the world are based upon our mind's utilizing these data from the senses. Hume, as with Descartes, held that what the mind was in immediate contact with were its ideas; the mind could not go beyond its ideas. Again, all that we know about the world is what is REPRESENTED on our TV screens. And Hume was skeptical about what kind of truth about the world our senses could give us. So far, Hume is not that different from Descartes. Let's go further to see the difference.

Hume was also interested in the sciences, but he was an empiricist, not a rationalist. A rationalist puts all his eggs in the basket of reason (Descartes), whereas an empiricist puts his eggs in the basket of experience (Hume). So, an empiricist will claim that knowledge has its origins in sense data, while a rationalist will claim that knowledge derives from the use of reason on certain types of ideas which are not derived from sense data (more about these ideas later). Hume, as I said, thought that knowledge, or at least what we could say we knew about the world, derived from the senses, whereas a rationalist, like Descartes, held that knowledge derived through the sole use of reason on innate ideas (ideas which the mind has within it to begin with and are discovered through the use of reason.) So, says Hume, were we to say that "There is a red tomato on the table," and claim the statement to be true, all that is needed to verify the statement is to check out the idea of the table in our minds to see if there is a red tomato on it. If our experiences verify the proposition, then we can claim that, as best we can tell, there is a red tomato on the table. That procedure was good enough for Hume on a day to day basis. But, Hume was bothered by something else which threatened to do away with science entirely.

Science was much more involved in its experiments than merely checking out whether or not there were red tomatoes on a table. Science was interested in cause and effect in the world. For example, suppose you saw a dark red stain on the wall. Someone told you that I had picked up a red tomato and had thrown it against the wall. In fact, the person claims to be able to prove without question that I had done it; he had videoed the event. Sure enough, there I am on the monitor hurling the tomato against the wall. You present the evidence against me to try and make me clean up the mess. However, I give an interesting reply in defense.

My reply is this. "OK, so you have a video of a number of events, but that doesn't mean that I caused the effect of the stain. What is on the video is a sequence of 'pictures,' but nowhere on the video is the picture or graphic indication that a causal event is in progress. If you know everything by sensation --you must have an IDEA from the senses of the item-- what sensation, what idea, do you have of the item CAUSE/EFFECT? I have never experienced cause/effect itself and I suspect no one else has either. I do not have nor have I ever had the experienced idea of cause/effect. Your charge against me is unfounded, because unless you can show that you can sense cause/effect itself, then you cannot say that it is a 'property' of the series of events on the video. There is no marker or cue on the series of events to indicate that they are linked together as cause and effect events. There is the marker (frame or experience) of me throwing the tomato. There is the marker or experience of the stain's being red; we can see the red stain on the wall. But, cause/effect is not like the attribute red that attaches to a subject. Thus, you cannot connect the event or frame of my throwing the tomato with the event or frame of a red mess on the wall because there is no sense data of cause/effect. There is no little tag, "cause," that attaches itself to the throwing frame; there is no tag, "effect," that attaches itself to the red stain frame. And, there is no tag, "cause/effect," which connects the two other tags together. Thus, you cannot prove that I am the cause of the mess and should clean it up. Too bad."

Let me follow through, here. I claim that you are wrong, that you never sensed the cause/effect relationship; all that was seen was a series of events. Of course, you go on to claim that you made the JUDGMENT that my hurling the tomato caused the mess; your judgment comes from your assessment of the sense data revealed in the video. But my damaging reply is, that judgment cannot be based on the ideas you have of the series of events. WHY? Because the one idea NECESSARY for you to claim a causal relationship is missing. Your judgment has no empirical foundation unless you can have an idea of cause/effect. Since no one can ever experience cause/effect itself, then there is no basis to support any causal claim about the world, much less the claim that my throwing the tomato caused the red mess on the wall. Unless there is the idea CAUSE attached to the idea of my throwing the tomato, and the idea EFFECT attached to the red stain on the wall, and the idea that this CAUSE is attached to that EFFECT, then you cannot say that I did it. You claim that you have the idea of cause/effect, but you cannot explain where you got the idea. I claim that the idea is bogus, since, for you, all ideas must come from the senses and you never have had the sensed idea of cause/effect. In virtue of all this, I can claim that maybe some hidden leprechaun threw the tomato and there are missing frames in the video.

The gist of my reply is serious for scientists who are empiricists. If science is based on the discovery of cause/effect relationship, and if that relation can never be experienced, then science becomes impossible. There would be no way to tell what was a cause and what was an effect, for there are no labels on the ideas in the mind anymore than there are on the video tape. The world cannot even be said to admit of cause and effect relationships at all. We may make judgments of cause and effect in our minds about our ideas and their sequences, but we cannot say that these judgments adequately portray what really is going on in the world. All of this led Hume to be very skeptical that anything we judged about the world from our experience of it was worth believing. Hume undermined the theoretical basis for scientific experiment.

10. A correspondence theory of truth, which matches ideas with things in the world, will not work as a way to get out of skepticism.

To make this problem more upsetting, let me take a little excursion into what "truth" might be. Take the sentence, "The sky is blue." Could Descartes or Hume say that the sentence, which claims to state a fact about the world, is true? No. Why? Because we can never get out of our theaters to see the real sky to determine whether or not it is blue. Descartes could not rely on a CORRESPONDENCE theory of truth; that theory states that a proposition is true if it is verified by facts in the world. Since Descartes says that we can never come into contact with the world, but only our ideas, a correspondence theory of truth is ruled out; we can never experience the world as it really is. There are no facts about the world that we can sense. We experience only our ideas and those ideas may not represent the real world at all. And since we never have cause/effect ideas or sensations even on our screens, then the prospect for viable science looks to be doomed.

A philosopher named John Locke (an empiricist) maintained a correspondence theory of truth. He maintained with Descartes that the mind was immediately in contact with its ideas, but he held that certain aspects of ideas truly represented the external world. Those aspects he called primary qualities. For example, were we to see a red cube on our screens, Locke would say that the proposition that "There is a cube in the external world," is true because the primary (mathematical) qualities of the cube in the external world match up precisely (are adequate to) the qualities of the cube idea in our minds; mathematics is exact and is the same in the objects of the material world as it is in the mental world of ideas. But, Locke went on to say that the material cube is not red; the redness of the idea of the material cube exists only in our minds. Our minds add that secondary quality red to the primary quality. The result is the idea of a red cube. The redness is caused by powers of the material cube, which powers are not themselves red at all. Locke is a modified simple empirical realist.

Our idealist friend, Berkeley, (points out the problem) that primary and secondary qualities are so inseparable in the mind that they could not be separable in the material world. But, if that were the case then perhaps the mind adds the primary qualities also. Consider, Berkeley tells us, that we do not have in our minds the idea of a cube but of a red cube. Moreover, the idea of the cube, the sense datum itself, has unequal sides, whereas a true mathematical cube does not. Could we even sense the true mathematical cube as it is; could we even sense it without it having some sort of color to be seen with? The answer to both questions, Berkeley says, is no. In fact, Berkeley goes on to conclude that because our ideas cannot be anything like a material world, and because we know only that ideas exists, it must be the case that only minds exist; there is no material world. Berkeley was a full-blown idealist; all that exists are minds. His criticisms of Locke's position are devastating; a modified empiricism will not do.

So, a correspondence theory of truth looks to be in trouble, given Descartes thesis that what we are in direct contact with (and only with) are our ideas. But, what could Descartes use for a criterion of truth?

11. A coherence criterion of truth will not get us out of skepticism.

He could use a COHERENCE theory of truth; a coherence theory states that an idea or belief is true if it coheres with the other ideas and beliefs we have in our minds.

Consider again the statement, "The sky is blue." Descartes could say that the statement is true because if we check our memories for ideas about the sky, and we always turn up ideas of the sky's being blue, and we have a belief based on that collection of memories, then the statement seems to cohere or agree with our memories and beliefs. In that case, we could say that it is coherent to believe that the sky is blue.

But, what if someone said the following? "The sky is not always blue, but changes to black or becomes invisible at night. In fact, the sky has no color at all; atoms, which make it up, have no color. The sky only appears blue because certain atoms refract light into different wavelengths which cause the color to appear in our minds during the daylight hours."

Uh-oh. Given what we have discussed about simple and critical realism, we could have two sets of coherent beliefs, but the two sets would be inconsistent with each other. One set concerns our ordinary perceptions and beliefs. We see the sky to be blue and we believe it to be blue. Were someone to ask us on a casual basis, "What color is the sky?" we would respond, "Blue." But, another set of beliefs concerns those which tend to try to make sense of these ordinary ideas through scientific investigation. That set of beliefs indicates that the sky is not blue or any color at all. Both sets are internally consistent or coherent, but put together, they are inconsistent. One set concludes that the sky is blue while the other set concludes that the sky is not blue --a glaring contradiction.

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