Alex Byrne and Skepticism About the External World

I recently read Alex Byrne’s paper Skepticism About the Internal World (PDF warning), and in this post I want to focus on the first part of the paper, where he talks about skeptical arguments about the external world. It’s not the main focus of the paper, but it sets the stage for his parallel arguments in the second part.

Cartesian Arguments

Byrne considers Cartesian arguments that suggest our sensory experiences are compatible with both a) there being an external world where, for example, I am sitting next to a warm fire, and b) having a dream that I am sitting next to a warm fire. Either hypothesis seems compatible with the sensory evidence, and so the evidence does not allow us to choose between a) (the sitting hypothesis) and b) (the dreaming hypothesis). So, according to this argument, we have some reason to be skeptical about the external world.

Byrne makes this into a more formal argument with the following premises and conclusion:

  • “P1. If you know that the sitting hypothesis is true, you know this solely on the basis of your evidence about your sensory experience.
  • P2. This evidence does not favor the sitting hypothesis over the dreaming hypothesis, and so does not allow you to know that the sitting hypothesis is true.
  • C. You do not know that the sitting hypothesis is true; that is, you do not know that you are sitting in a chair.”

Dogs and Rabbits

This is the Cartesian argument, and Byrne wants to show that at least one of the premises is false, so as to avoid the conclusion. In this paper, he focuses on P1. Here is how he goes about it. Byrne states that the template for P1 is that if you know hypothesis H, it is on the basis of evidence E. So H is inferred from E, which in turn means that E is known.

Byrne then gives the example of a non-human animal such as a dog:

“They have sensory experiences (or so we may suppose) but there is not much reason to think that they know that they have sensory experiences. Knowledge of one’s own mind requires a sophistication that dogs appear to lack. So if a dog knows that there is a rabbit behind a tree by using its eyes, it is not on the basis of evidence about its sensory experiences. And if evidence about sensory experiences is not needed for a dog to have environmental knowledge, it isn’t needed for us to have environmental knowledge either. You could know that you are sitting in a chair without appealing to evidence about your sensory experiences, and presumably you do. Hence P1 is false.”

Byrne concludes that section by stating that proponents of the Cartesian argument will have objections, but that he won’t consider them in this paper.

These are the objections that come to my mind:

Objection One

It seems that a bait-and-switch has occurred, where Byrne is now stipulating that P1 requires a sort of meta-awareness or higher-order processing of the sensory experience. And since that meta-awareness is absent in dogs, it must be (or likely is) absent in us as well. But that’s not what P1 required. It didn’t say “you know this solely on the basis of your meta-awareness of your sensory experience.” So it seems Byrne is requiring “evidence” to mean precisely this sort of meta-awareness. At the very least, Byrne needs to state what he thinks it means to “know E.”

Objection Two

In the dog and rabbit example, Byrne is being inconsistent about whether the dog “knows” things. If the dog doesn’t know the evidence about its sensory experience, why should we say that it knows the rabbit is behind a tree? Does he believe that the dog has some higher-order mental representations regarding the rabbit behind the tree? Why should we say that it’s lacking this type of capability regarding its own mind but not regarding the rest of the world?

Again, this isn’t the main focus of the paper, but he does use it as the basis for the main part of the paper, so it would be good to see him consider some of the objections.

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