I’ve been watchinig the first season of the new Dr. Who. There’s an episode called “Aliens of London” that involves a pretty interesting Gettier case.

Dr. Who Gettier Case
Aliens are invading Earth. Part of the alien plot involves making people think there is an alien invasion in a way that is much different from the way in which they are actually invading. They stage a crash landing with a genetically mutated pig that looks alien-ish. Reporters on the BBC start reporting about alien invasions. People in parliament are preparing for alien invasion. There’s some secret protocol on alien invasions that gets brought to the fore.  So, people think that aliens are invading. (Aside: strictly speaking this may not be enough to justify alien invasion, but we could amp up the evidence a bit if you’re worried about that).

The real alien invasion has been taking place from within body snatcher style. Aliens have been assassinating key persons in government and wearing their bodies as skin suits. They use the panic to finalize their plans, now that they look like government officials.

Claim One: Some persons in this episode have a justified true belief that aliens are invading.
Claim Two: Those persons lack knowledge, they are in a kind of Gettier case.

What Different Theories of Knowledge Must Say
We have then a case of justified true belief that isn’t knowledge. I’m interested in what other modified theories of knowledge that are alleged to handle Gettier cases must say about this. Let’s pick some arbitrary person in the Dr. Who episode that would make claim (1) and (2) true. Call that person, Bob. There are a few modified theories of knowledge (I have in mind some JTB+4th condition theories) that get the above case right. They would hold that Bob does not know that aliens are invading.

In this post I want to warm-up with sensitivity theories of knowledge.

Sensitivity Theories of Knowledge
Sensitivity theories come in two stripes. Some people go for an analysis of knowledge that is cashed out wholly in terms of sensitivity, and some go for a sensitivity principle that gets tacked on to JTB as a kind of fourth condition on knowledge. Here are two examples of both strategies.

Sensitivity Analysis of Knowledge
S knows that P iff If P weren’t true, then S would not believe P.

JTB+Sensititivity Analysis
S knows that P iff (i) P is true, (ii) S believes P, (iii) S is justified in believing P, and (iv) if P weren’t true, then S would not believe P.

What’s interesting about both versions is that they seem to get the Dr. Who Gettier case wrong. If it weren’t true that aliens were invading, then Bob would not believe it. Why? Because in the nearest possible world where aliens aren’t invading, there is not a faked alien invasion (I think).

OK. That shouldn’t be a terribly surprising result. There are loads of Gettier-esque problem cases for a simple sensitivity account of knowledge. However, there’s something else I like about this case. While there are Gettier-esque counterexamples to Sensitivity Analyses of knowledge, many involve some weird far-fetched causal deviance. Originally, these sorts of cases were used against the causal theory of knowledge (S knows that P iff S’s belief that P is caused by the fact that P).

One such example is as follows:

Falling Down the Stairs Case
Imagine Bob fall down the stairs and gets bumped on the head, it erases his short term memory so he doesn’t remember falling down the stairs via the normal mechanisms. However, it causes a swelling in his brain that causes the belief that he fell down the stairs.

Technically, Bob’s belief that he fell down the stairs is caused by the fact that he fell down the stairs. Problem for causal theories. However, this is also a problem for Sensitivity Principles. If Bob hadn’t fallen down the stairs, he wouldn’t believe that he fell down the stairs. So,  sensitivity accounts of knowledge the get falling down the stairs case wrong too.

Deviant Causal Chains to the Rescue?
Some think that there something infelicitous about this kinds of causal chains involved in these cases. It’s a deviant causal chain. Causal theories of anything usually encounter some puzzling case where a deviant causal chain is involved. So, proponents of sensitivity (or causal theories for that matter) might point to partners in crime and all we need is some demarcation theory to distinguish these deviant causal chains from the ordinary sorts of causal chains we had in mind when we constructed our theory and we’ll be all set.

However, the alien case doesn’t seem to involve a deviant causal chain in the same way that the brain lesion case does. The faked alien invasion was definitely part of the real alien invasion. It was designed by the aliens to make people think they’re being invaded. So whatever is meant by deviant it’s far from clear that the faked alien invasion is playing a deviant/accidental role in bringing about the belief in the way that the brain swelling does in the falling down the stairs case.

That’s why I think this Dr. Who case might be a more interesting Gettier-style puzzle for sensitivity theories.

Up next: Safety Theories (if I think I have anything interesting to say about how Safety theories might handle this case)