Friday, March 13, 2009

Lying about PowerPoint

In chapter 6, Williamson says that sometimes when he is teaching his students about Gettier cases, he says certain things to them so that they are actually in a Gettier case themselves. But I'm wondering whether what he says to them actually succeeds in Gettierizing their beliefs. He says he starts off by telling them:

(1) The only time I've used PowerPoint in the past it was a complete disaster.

From this they naturally come to believe:

(2) Williamson has never successfully used PowerPoint.

(2) is in fact true, and they seem to be justified in believing it (given that they have no reason to distrust his testimony in (1)), but they don't know (2) because the belief it represents is based on a lie. In fact, Williamson has never even tried to use PowerPoint and thus he says that (1) is false. Since they base (2) on something false, it looks like they don't know (2) despite the fact that it is a justified true belief.

But is (1) false? I guess it depends on what's being said. If what he is saying is this:

There exists a time at which I used PowerPoint and my using PowerPoint at that time was a disaster,

then it is indeed false. But if what he is saying is this:

Every time I've used PowerPoint in the past it has been a disaster,

then it looks vacuously true given the peculiarity of the universal quantifier.

Of course, maybe what this shows is that Gettier situations can arise even if the belief in question isn't based on a false belief. And, in any case, Williamson could just as well start his classes by saying, "I have used PowerPoint once before and it was a failure". So I'm not questioning the possibility of Gettierizing students...I'm just wondering whether the case as he presented it does the trick, and what it might tell us about Gettier cases even if it does.


Blogger Joshua said...

Every Gettier style counterexample to the JTB analysis of knowledge falls into one of two categories. In the first category are cases that involve an individual who bases his belief on a falsehood. These cases also often involve deductive inferences. So, from the false belief that Jones will get a the job Smith applied for and the true belief that Jones has five coins in his pocket, Smith infers that the man who will get the job he applied for has five coins in his pocket. This happens to be true because Smith himself will get the job and he also has five coins in his pocket.

But, if all Gettier style examples involved inferences from false beliefs to true beliefs, then it would be easy to solve the Gettier problem. The really hard cases involve inferences from true beliefs to true beliefs. These inferences are not truth preserving inferences. So, for example, Russell looks at a clock that is stopped at 12:00. Russell infers from the true belief that the clock says that it is 12:00 to the true belief that it is 12:00. But, this inference is not truth preserving since, obviously, a clock can say that it is 12:00 without it actually being 12:00.

What all this indicates is that the solution to the Gettier problem may involve at least two elements. One element might be as simple as this: No believe inferred solely from a falsehood is known. Another element will eliminate cases that involve non-truth preserving inferences to things that happen to be true. This might be some kind of safety condition.

8:18 PM  
Blogger Lewis said...

I think your universally quantified analysis of what he is saying is at odds with standard semantics for "The only time". You universally quantified statement is entailed by what Williamson said, but it is not itself the semantic value of his utterance.

7:37 AM  

Post a Comment

<< Home