Philosophy 159: Stroud Chapter 2

Chapter 2. Stroud versus Austin

In Chapter 1, we were discussing Descartes' claim that knowing you're not dreaming is a requirement for knowing anything about the external world.

Of course, in everyday life, or in a legal trial or a science lab, we don't ordinarily insist that you know you're not dreaming before allowing that you know anything. So does Descartes' requirement, enshrined in Stroud's Principle or in one of the Closure Principles, raise our ordinary standards for knowledge in an artificial way? (Compare the artificially strict definition of "physician" that Stroud discusses.)

Austin thought that the skeptic does distort our ordinary requirements for knowledge. He makes them out to be more stringent than they really are. So Stroud spends a lot of this chapter setting out Austin's view, and then arguing against Austin, in defense of the skeptic.

Stroud discusses three elements of Austin's view.

On pp. 45-5, he discusses Austin's claim that, to raise a legitimate doubt about someone's knowledge claim, you have to suggest some specific way in which the subject might be mistaken. (Descartes does seem to do this.)
On pp. 46-8, he discusses Austin's claim that dreams are qualitatively distinguishable from waking experiences. (According to Austin, dreams always have a special "dream-like quality.")
On pp. 48-53, he discusses the most important element of Austin's view. This is Austin's claim that you only need to rule out some possibility if there's some special reason to believe that it does now obtain.
If you have positive evidence that you are a brain in a vat (like the guy in the Pollock and Cruz story), then you need to rule that possibility out, before you can know anything about the external world. But the ordinary person doesn't have any evidence that he is a brain in a vat, so he can know things about the external world (assuming those things are true), without having to rule out the possibility that he is a brain in a vat.

So now we have two accounts of knowledge.

Descartes requirement on knowledge: In order to know anything about the external world, you have to rule out the possibility that you're dreaming.
Austin's weaker requirement: If there's some special reason to believe you are dreaming, then you have to rule out the possibility that you are dreaming; otherwise not.

Which one should we accept?

Stroud argues in favor of Descartes' requirement (see Stroud pp. 57-64). He begins by making an important distinction. We need to distinguish between the questions:

Is it true that such-and-such?
Is it appropriate or reasonable to say that such-and-such?

Some things can be true even though it wouldn't be appropriate to say them. For instance, suppose that you know that Mary is hard at work in the office. Then it's true that she's either hard at work in the office, or still home in bed. But if the boss asks you where Mary is, it wouldn't be appropriate for you to say "She's either hard at work in the office, or still home in bed." That's true but in that situation it wouldn't be appropriate to say it. Saying it suggests that you don't know where Mary is, or that she often stays home in bed when she ought to be working, or something like that.

Also, some things can be appropriate to say even if they're not, strictly speaking, true. Some philosophers argue that no physical surface is ever really flat, because it will always have microscopic bumps and irregularities. The same philosophers argue that no physical container is ever really empty, because it will always contain bacteria, specks of dust, and the like. But even if it's not strictly speaking true that the blackboard is flat, it can often be appropriate to call it "flat." Suppose you're flying a plane, and the engines fail, and the copilot says, "We need to find a flat place to land the plane," wouldn't it be appropriate to think of things as flat as the blackboard as being "flat"? Even if it's not strictly speaking true that they're flat. If you move all the goods out of the warehouse, wouldn't it be appropriate to call the warehouse "empty"? Even if there are still some old beer cans and cigarette butts laying around? It's often appropriate to use "flat" and "empty," even if, by the standards these philosophers insist on, it's not really true that the things we're talking about are flat or empty.

Now much of Austin's argument for his weaker requirement for knowledge goes as follows. He argues that it would normally be inappropriate to challenge a person's claim to know that P, on the grounds that she hasn't ruled out some remote possibility like dreaming. Stroud accepts that, but he argues that it might nonetheless be a requirement for knowing P, that you rule out possibilities like dreaming. When someone satisfies Austin's weaker requirements, that may make it appropriate or reasonable to say that they know--and inappropriate to deny that they know--without yet really making it true that they know. This may be a case like "flat" and "empty." You never really know, because you're never really in a position to rule out all the alternative possibilities. But often it's appropriate to say you know, even though it's not strictly speaking true.

Stroud suggests that there will often be good practical reasons why we say that people "know," even though they haven't ruled out all the possibilities that he thinks, strictly speaking, they need to rule out in order to have knowledge. He illustrates this with the example of the airplane spotters (pp. 67ff.).

In that example, spotters are trained to watch planes flying overhead and classify them as Es or Fs. If the planes have features x, y and w, they class them as Es; if they have features x, y, and z they class them as Fs. However, nobody bothers to tell the spotters that Gs also sometimes have features x, y, and z. It's not important that they know this, since Gs rarely fly overhead, and if they do, it's not a big deal if they get mistaken for Fs. Plus from the ground it's basically impossible to tell Fs from Gs, anyway.

Now if a spotter sees a plane with features x and y, clearly that is not enough for him to know it's an F. It might also be an E. He has to inspect the plane to see whether it also has feature w or feature z. But Stroud says that even if the spotter determines that the plane has feature z, that is still not enough for him to know it's an F. It might also be a G. He would have to rule that possibility out, too, if he's really to know that the plane is an F. Perhaps he's close enough to knowing it's an F for our present intents and purposes. Perhaps it's reasonable to say that he knows it's an F. (It's clearly reasonable for him to say that it's an F, and that he knows it's an F; since no one told him about the Gs.) But strictly speaking, Stroud thinks, we wouldn't want to say the spotter knows the plane is an F. Any more than we'd say he knows it's an F if he hadn't yet ruled out the possibility that it's an E.

Now, the skeptic sees our position with respect to his skeptical hypotheses (involving dreaming, evil demons, or brains in vats) as analogous to this. There may be good practical reasons why we don't try to eliminate, or even consider, far-out possibilities like the ones the skeptic discusses. But strictly speaking, those possibilities do have to be ruled out, if we're really to know the things we say we know. Just as the airplane spotter would have to rule out the possibility that the plane he sees is a G, if he's really to know that it's an F.

If this story is right, then the skeptic is not distorting our ordinary understanding of "knowledge." He's just relying on a phenomenon which is already implicit in cases like the airplane-spotter case. He's not changing the meaning of "knowledge," or imposing any new or artificially high standards. He's just pointing out that sometimes we think it's reasonable to say someone knows (like the spotter who doesn't know the difference between Fs and Gs), even if in fact there are possibilities that person hasn't ruled out, and so it's not really true that they know. The skeptic thinks this is exactly our situation with respect to our beliefs about the external world.