Skepticism concerning colours?

By Hendrik van der Breggen
(The Carillon, December 16, 2010)

Skepticism concerning colours?

I hope that readers are not tiring of my recent barrage of columns wherein I challenge skepticism concerning our knowledge of the external world. I am convinced (and convicted) that knowledge of the world external to our minds is important. Why? Because we can know (albeit fallibly and non-exhaustively) some truths about the world—and these help us to know, with further investigation, some truths about God.

In an attempt to put another nail in the coffin of skepticism concerning our knowledge of the external world, today I will address yet another skeptical objection, namely, the how-do-you-know-I-see-the-same-colour-as-you objection. The idea behind this objection is that because I don’t know that you see the same colours of the external world as I do, I should be skeptical of my knowledge of the external world (at least in terms of colour).

Should we succumb to the how-do-you-know-I-see-the-same-colour-as-you objection? I think not. Here are four reasons which work together as a cumulative case argument to diffuse the objection’s apparent logical force.

Reason 1. From the fact that I don’t know what Joe sees, it doesn’t follow logically that I don’t know what I see. Yes, I do not know what goes on in Joe’s mind, but that doesn’t mean I don’t know what I know. (Think about it.)

Reason 2. From scientific investigation of the world, we know the physical world well enough to realize (a) that a colour has a particular wave length which distinguishes it from other colours, and (b) that we humans are very similarly constructed (physically), and so (c) we have some prima facie good reasons for thinking that Joe is seeing the same colour as I am.

[A brief discussion of prima facie may be appropriate here. Prima facie is Latin for “first face” or “on its first appearance.” In ethics, to say that action X is one’s prima facie moral duty means that X is one’s obvious moral duty and so ought to be done, though X may yield to a more pressing or weightier moral duty Y. For example, if X means keep my promise to meet my friend for lunch, and if Y means save a child drowning in the wading pool, then, in the absence of circumstances that require Y, I ought to do X. When prima facie is used in epistemology (theory of knowledge) it means that a matter P appears self-evident or obviously true and should be accepted as such, unless a more pressing consideration Q outweighs it. For example, if P means I know I have a nose on my face, and Q is a good reason for thinking I don’t have a nose on my face, then, in the absence of Q, I ought to go with what’s obvious, namely, P, that I know I have a nose on my face.]

So, in the absence of good reasons for thinking that Joe isn’t seeing the colour as I do, and until we know of a more pressing reason to think otherwise (e.g., good evidence that Joe is colour blind), we should go with what seems obvious, i.e., that we see the same colour in the same way.

Reason 3. To think that the logical possibility of Joe’s seeing a different colour constitutes good grounds for thinking that the colour is in fact seen differently by Joe and me is to confuse bare logical possibility with epistemic probability/plausibility.

[At this juncture, a discussion of the distinction between bare logical possibility and epistemic probability/ plausibility may also be appropriate. To assert a logical possibility is merely to assert a description that hasn’t got a contradiction in it. For example, that the moon is made of cheese is a logical possibility. Of course, the mere assertion of this logical possibility isn’t enough to ground our belief that it is actually so. On the other hand, epistemic probability/plausibility means that X is logically possible and we have other grounds for thinking X is true. So, for example, if the claim that the moon is made of cheese is epistemically probable/ plausible, then not only is it possible that the moon is made of cheese, but also we have actual evidence of moon rocks containing significant traces of Parmesan.]

Reason 4. Following an insight from the philosopher Ludwig Wittgenstein (1889-1951), we can also point out that to imagine a doubt isn’t really to have that doubt. We can imagine, say, that the Statue of Liberty is a robot—but that’s not really to believe it actually might be a robot. That is, we can imagine the doubt that the statue isn’t really a statue, but that’s not actually to doubt it’s a statue.

So, yes, we can imagine that Joe and I see different colours, but that doesn’t mean we should truly believe that Joe and I might in fact be seeing different colours. Simply put: imagining isn’t doubting. To think otherwise is to confuse two distinct cognitive categories.

That’s enough about skepticism (for now).

Christmas is a time when we celebrate the truth concerning the God who allows us to know Him. God has revealed Himself not only in the creation itself but also, and most clearly, in the God-man Jesus Christ—Emmanuel, God with us.

May the beautiful colours of the season add to our joy!

Apologia columns on radical skepticism:

(Hendrik van der Breggen, PhD, is assistant professor of philosophy at Providence College, Otterburne, Manitoba, CanadaThe views in this column do not always reflect the views of Providence.)

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