Dialogue on Knowledge and Reality

© by Jan Garrett

Revised: October 2, 2007

Characters in the Dialogue on Knowledge and Reality

Note that these positions are concerned with the possibility of knowledge, or true thoughts, about realities outside the mind of the thinker. They are simplified versions of views introduced among classical Greek philosophers from ca. 500 to 250 B.C.E. I have been partly influenced by T. Irwin's Classical Thought (first edition), chapter 4. Note that the definitions of terms like "metaphysical realism," etc., vary to some extent among writers, so those who use them should always state how they define them.

Rea, the metaphysical realist who holds a correspondence theory of truth
There is a reality external to the mind, and what makes a thought true is correspondence or agreement between the thought and reality.

Eve, the na´ve realist
External reality is knowable. We can form true thoughts about it. It is more or less as it appears to the senses, when our sense organs are functioning normally and we examine things carefully. (Sometimes this view is called naive empiricism.)

(Although Aristotle is not a na´ve realist, in some of his inquiries, e.g., biology, he seems to presuppose a data-gathering phase of research that corresponds to Eve's approach to reality.)

Sy, a critical or scientific realist
Reality is knowable. We can form true thoughts about it, but not all our thoughts about it are accurate.

Naturalist version (for example, Democritus' philosophy; Sy's critical realism is of this type): Some sense perceptions reveal what is out there in the physical world; we can have knowledge of it. Only what is quantifiable in nature can be genuinely known. Size and shape and relative position and motion are features of reality. Color, sounds, taste, odor, and tactile qualities like hard and soft, hot and cold, are not. (If Eve's position is called naive empiricism, then Sy's might be considered a form of critical empiricism.)

Platonic version: Our sense perceptions do not give us direct access to reality (i.e., the Forms), but we can come to know it by use of the proper method, i.e., dialectic.

There might be still other versions.

Neal, the nihilist (inspired by Gorgias the Sophist?)
We have and can have no genuine knowledge of the "external world." Since knowledge correlates with reality, we can conclude that there is no reality "out there."

Schuyler, the skeptic
It is not reasonable to claim knowledge of an external world. Still, an external reality may well exist.

R.E. Lativ, the extreme relativist
Appearances are true, real, or known relative to a perceiver, theorist, or group.

(Something like this view is attributed by Plato, in his Theaetetus, to Protagoras. R.E. holds the "perceiver" version of this theory.)

The Dialogue

Eve and Rea are standing around chatting, when Schuyler comes up.

Schuyler. Hey Eve, Rea, what do you know?

Eve. Quite a bit, Schuyler. I just returned from my botany expedition to the Costa Rican rainforest. We got up close and personal with lots of plants I had only seen before in textbooks.

Sch. How does that give you knowledge?

Eve. A good scientist will use all her senses, sight, smell, touch, hearing (although plants don't make as much noise as animals, of course).

Sch. So your senses never mislead you?

Eve. Not if they're healthy and not if the lighting is normal. It's better to look at plants in the daylight than at dawn or dusk.

Sch. Why this preference for normal light? Isn't that just light humans are used to? Why should we assume that such light reveals things as they really are?

Eve. I'm not sure I can answer that, Schuyler. Here's Sy. He's a physics major. Let's see what he thinks.

Sy. I don't think that colors or sounds or tastes reveal things the way they really are. We experience colors, sounds, etc., when something moving from what we experience collides with our sense organs. Colors, sounds, etc. are the results of interactions, not what's really out there. The ancient atomist Democritus knew this already. He said that what's really out there are the sizes and shapes and motion properties of atoms. Today we say that what's really out there are the measurable and quantifiable qualities of waves and particles and force fields. We can come to know these measurable, quantifiable qualities.

Eve: But I feel confident that colors are really there, when I see them.

Sy: Think about it, Eve. Some people see a light and think it's green, others think it's red. People taste wine as sweet when their body is in one condition, sour when it's in another. If you put your hand into warm water before putting it into luke-warm water, the latter appears cool. If you put your hand into cold water before putting it into luke-warm water, the water appears warm. I draw the conclusion that our perceptions of colors, tastes, hot and cold, etc. are unreliable.

Sch: You make a distinction between what people like Locke called ideas of secondary qualities (like color), which don't agree with the realities that cause the ideas, and ideas of primary qualities like length and shape, that do agree with the realities that cause them.

Sy: Yes, I've heard it put that way.

Sch: Tell me, honestly, Sy. When you measure what seems to be the same thing, do the results always come out the same?

Sy: No, there is often some range of variation.

Sch: Do you assume that what you are measuring has changed?

Sy: Not always, sometimes we figure the condition of the observer is slightly different from what it was before.

Sch: Then the evidence about quantitative aspects of reality is a bit ambiguous.

Sy: I suppose so.

Sch: You know those line drawings in which two parallel lines, which you have measured to be equal, say, 2" in length, are given wedges at the ends. In the one case, the wedges point out from the ends, in the other they point in. Anyone looking at the lines without having been prepped in a special way "sees" that one line is longer, right?

Sy: Yes, they seem to.

Sch: But to somebody who has just gone through the effort to measure them with a ruler, they're equal.

Sy: Yes.

Sch: my point is that the evidence for the perceptual stability of quantitative aspects of reality is ambiguous no less than the evidence for the qualitative aspects of reality.

Sy: But what if we go deeper, as physicists or philosophers of nature have done ever since the beginning of natural science? If we do, we discover a reality that is hidden from direct perception but which explains what we perceive. The ancient atomists, for instance, taught that reality was composed of indestructible atoms moving through the void and being rearranged. With the aid of this theory they could explain both the quantitative aspects of things we observe with the senses, and the qualitative aspects we observe, such as redness and sweetness, even though what causes our perception is not redness or sweetness in external objects.

Sch: The problem for that strategy is that the physicists themselves disagree about ultimate reality. Some like the atomists teach that reality is composed of indivisible material solids. Others, like Socrates' contemporary Anaxagoras, held that the material elements were divisible, potentially, all the way down, that is, there was no such thing as a smallest possible quantity of water or gold. What these examples show is that just as there is no agreement about the information presented by the senses, so there is no agreement about the information presented by scientific theory.

Neal. Hello, I was just listening to your discussion. If I may I'd like to say I agree with where Schuyler is going, and point out what it means.

Sch: Please do.

Neal: What it means is that there's no there there. There's no reality waiting to be known, nothing real. What there is is perception, sometimes of this, sometimes of that. The dream of botanists like Eve and science majors like Sy is wasted. You can't get in touch with a reality outside you. All you get is perception.

Sch: There is another possible interpretation of what we've agreed upon.

Neal: What's that?

Sch: While I agree with you that what you get is perception, and not reality, reality might still be out there. It's just that we have no access to it. It does not reveal itself to us as it is in itself.

R.E.: Is that why you're called a skeptic, Schuyler, because you claim we cannot know what reality is.

Sch: Yes, that's why. We skeptics don't deny the existence of an external reality. We just believe it's beyond human capacity to know reality.

Rea: I've not said much, but I assure you folks I've been listening carefully. It's so nice to have so many people who agree with me.

Neal: I wouldn't have thought it possible in this crowd to have much agreement at all.

Rea: Well, listen up. My view is that a proposition or thought is true only if it corresponds with reality. Let's see who agrees with me.

First, Eve agrees with me because she thinks that colors and sounds, along with sizes and shapes and so on are out there in the real world independent of our perceptions, and that we can think truly about them and express our thoughts about them with statements that correspond to the external reality. Right, Eve?

Eve: Right so far, Rea.

Rea: And Sy agrees with me because he thinks that sizes and shapes and so on are there in the real world independent of our perceptions and that we can think truly about them and express our thoughts in statements corresponding to the external reality. Right, Sy?

Sy: Right again, Rea.

Rea: Schuyler agrees with me too. Although he does not think we can know anything about the external world, the reason he thinks that we cannot know it is that we cannot be sure that any of our thoughts agree with a reality independent of us, even though such a reality may exist. But I think that he would say--and he can tell me if I'm wrong--that if somehow it were possible for us to think thoughts that agreed with external reality, they would be true thoughts.

Sch: Right again, Rea.

Neal: What about my view?

Rea: Well, you say there is no reality, but that's because you too think that if there were knowledge it would involve agreement between some thought and an external reality. Because you reject the possibility of knowledge, you also deny reality. But the very ideas of knowledge and independent reality are still linked in your mind.

R.E.: All of you not only agree with Rea about truth, you also make a sharp distinction between appearance and reality. Even Eve admits our senses mislead us in dim light, so under those circumstances we don't get reality, only appearance. Sy admits that our senses only give us appearances when all we notice is color or sound or taste, and fail to penetrate to the measurable physical reality out there according to him. Schuyler thinks that we cannot know reality, although we do perceive what appears to us. And Neal thinks there is no reality, although he does not deny that we are conscious of appearances. And Rea's metaphysical realism also commits her to such a distinction, unless I am seriously mistaken. Her idea of a reality independent of the mind would make no sense if she did not also have the idea of appearances, that is, perceptions, that sometimes do not correspond to reality.

Rea: You're right, R.E.. I do make a distinction between appearance and reality.

(Eve, Sy, Schuyler, and Neal also admitted that R.E. had described their positions accurately.)

R.E.: Ah, but you're all wrong about that distinction. There isn't any. Reality is just what appears to people.

Rea: Or at least that's the way it appears to you.

R.E.: That I can't deny. I'm the only one here who does not accept a distinction between reality and the way things appear to me. I think Protagoras got it right when he said, according to Plato's Theaetetus, "The human being (by which he meant the human perceiver) is the measure of all things, of those that are, that they are, of those that are not, that they are not."