Showing posts with label Sensory Skepticism. Show all posts
Showing posts with label Sensory Skepticism. Show all posts

December 16, 2010

Skepticism concerning colours?

APOLOGIA
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, Canada. The views in this column do not always reflect the views of Providence.)
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September 23, 2010

Radical Skepticism (Part 2 of 4)

APOLOGIA
By Hendrik van der Breggen
The Carillon, September 23, 2010

Radical Skepticism, Part 2 of 4: Sensory Skepticism

 Radical skepticism concerning the external world is the philosophical view that we cannot have accurate knowledge about the physical reality that exists outside our minds. If radical skepticism were true, then we could not know the external world. Moreover, we could not know the external world's revelation of God, whether God's revelation is via the heavens declaring His glory or via Scripture's pages presenting reports of empirical evidence about Jesus Christ.

Should we be persuaded by radical skepticism? I think not.

There are at least four types of radical skepticism. Last time we looked at funky/pop skepticism. Today we will look at sensory skepticism.

Sensory skepticism tells us that we cannot know the external world because our senses deceive us. (This species of skepticism, like the dream hypothesis discussed in my previous column, is inspired by the philosopher René Descartes [1596–1650].)

To understand the force of sensory skepticism, consider the following examples. While rowing my boat, I put an oar into the water, but then the oar appears bent. While walking in the countryside, I see a flat wall on a distant farm building, but as I get closer the wall turns out to be curved. While strolling along railroad tracks, I see that the metal rails look straight and parallel to each other, but then on the horizon they appear to meet. While driving my car on a hot summer day, I see water on the road ahead, but as I continue to drive I observe that the road is dry. While volunteering as a lab rat for a psychology researcher, I see a red six of hearts as the researcher flashes a playing card, but later the researcher reveals that it was a red six of spades.

Clearly, my senses do deceive me. Therefore (or so the argument goes), my senses should not be trusted.

There are three reasonable criticisms that can be set out against radical sensory skepticism.

First, always does not follow logically from sometimes. The fact that we are sometimes deceived by our senses does not mean that we are always deceived by them.

Second, to know that our senses sometimes deceive us requires that they sometimes or often do not. Indeed, for us to discern that I mistakenly think that the oar is bent, that the wall is flat, that the tracks do not remain parallel, that the road is wet, or that the card is a red six of hearts requires that we have clear and accurate sensory knowledge. It presupposes that we know—accurately—that the oar is in fact straight, that the wall is in fact curved, that the tracks are in fact parallel, that the road is in fact dry, that the card is in fact a red six of spades. The argument of the sensory skeptic, then, requires as legitimate and true what it purports to show is not legitimate and true. It self-refutes.

Third, because the argument for sensory skepticism very apparently fails, our senses’ prima facie veridicality—that is, their very apparent truthfulness—remains. In other words, the burden of proof belongs to those who deny the obvious, so the senses are innocent until proven guilty.

It is reasonable, therefore, to go with what our senses tell us about the world, as long as we have no overriding reason to doubt them, and as long as we are careful.

How does this relate to Christianity? Significantly, it turns out that the reports concerning Jesus' resurrection tell us that the witnesses carefully used their senses to ground their belief. According to the New Testament record, the witness testimony has do with that "which we have heard, which we have seen with our eyes, which we looked upon and have touched with our hands" (1 John 1:1). Also, this record tells us that the resurrected Jesus appeared to individuals and variously sized groups (1 Cor. 15:3-8), was seen to eat fish (Luke 24:41-43), invited physical touch (John 20:27), plus talked with the witnesses (Matthew 28:9-10, 16-20), all over a period of several weeks (Acts 1:3). The witnesses were so convinced by the proofs of the physical reality of what their senses perceived—proofs that Jesus was physically alive after His death—that they testified to the resurrected Jesus in spite of persecution and suffering.

If radical sensory skepticism were true, then the witnesses' suffering for the truth of what they heard, saw, and touched—so we could reasonably believe their reports—would be in vain. Happily, radical sensory skepticism is not true.

Next: Kantian skepticism.

P.S. The above column is a slightly revised excerpt from my larger article, "Reasonable Skepticism about Radical Skepticism," Christian Research Journal, Volume 31, Number 5 (2008): 30-38.

Apologia columns on radical skepticism:

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