Tuesday, December 20, 2011

On Lois Lane and rationality

Lois Lane has the following two beliefs

(1) that Clark Kent cannot fly, and that Superman can fly.

Yet Clark Kent and Superman are identical. Substituting ‘Superman’ for ‘Clark Kent’ in the first belief gives us the beliefs

(2) that Superman cannot fly, and that Superman can fly.

Clearly it is irrational to hold the beliefs characterised by (2). Does this mean that Lois has irrational or illogical beliefs in believing (1)? Or is the inference from (1) to (2) invalid? Contra: the beliefs characterised in (1) are clearly not irrational. For we base our beliefs on evidence. The evidence given to us in the Superman stories suggests that Clark Kent and Superman are identical. The reader is always shown evidence that Clark Kent is Superman, by means of scenes showing him changing from his office suit and glasses to his Superman costume, without glasses. The same stories show us that Lois Lane does not have the benefit of this evidence. She is looking the other way, or is looking for shoes or handbags while Clark is changing his costume. Therefore

(3) The reader of the stories has evidence that Clark Kent is Superman

(4) Lois Lane does not have evidence that Clark Kent is Superman

Therefore, I argue, it is not irrational for Lois to have the beliefs expressed by (1). It is not irrational to believe that of which one has no evidence to the contrary – even though other people, such as the reader, have evidence to the contrary. Therefore the inference from (1) to (2) is invalid.

Note, and this is actually is my main point against Eric’s position here, that it is invalid for exactly the same reason that the following inference is invalid.

(5) Lois Lane has evidence that Superman can fly, therefore she has evidence that Clark Kent can fly.

The puzzle about substitution and belief statements is the same as the puzzle about substitution and evidence statements. Even though Clark Kent is identical with Superman, the evidence that Clark Kent is Superman is different from the evidence that Clark Kent is identical with himself.

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9 Comments:

Blogger Anthony said...

>> Lois Lane has the following two beliefs...

Honestly I don't think we should be deriving logical arguments from fiction. *Can* Clark Kent fly? *Is* Clark Kent identical to Superman? I don't even think these questions have definite answers.

9:29 pm  
Blogger J said...

Superman = Clark Kent (whether known or not).

Superman flies -> Clark Kent flies.
Superman does fly.

Ergo, Clark Kent flies.


Q.E. f-ing D.

1:02 am  
Blogger Anthony said...

Perfectly valid, J, though not sound. There is no Superman.

Interestingly, though:

X believes that Superman = Clark Kent.
X believes that Superman flies -> Clark Kent flies.
X believes that Superman does fly.
Ergo, X believes that Clark Kent flies.

It seems to work fine so long as you keep the "X believes" in front of everything, at least on the assumption that X is rational (in fact, this is probably a good definition of "X is rational"). It's when you start mixing "X believes P" and "P" that things get out of whack.

2:33 pm  
Blogger Anthony said...

And more specifically, it's when you start changing *context* that things get out of whack.

X believes that A is B, in the context of X's beliefs, is not the same as X believes that A is B, from the context of your own beliefs (which is the context which one generally means when one says "A is B").

3:46 pm  
Blogger J said...

Googled arguments for a few days, eh.
The technical answer to that is, No shit. However, many logicians--Lewis Carroll for one--are not stopped by mere "existential import."

you forget again that "believe" doesn't belong in formal arguments.

4:01 pm  
Blogger Anthony said...

I forget that "believe" doesn't belong in formal arguments? What is this "forget" you are talking about?

6:10 pm  
Blogger Tristan Haze said...

I like the point that 'X has evidence that ...' is an intensional context!

Anthony,

'Honestly I don't think we should be deriving logical arguments from fiction. *Can* Clark Kent fly? *Is* Clark Kent identical to Superman?'

I can't see any problem here. The story we are playing along with in these discussions is pretty definite about Clark Kent being Superman, and that individual being able to fly.

J,

'you forget again that "believe" doesn't belong in formal arguments.' - What do you mean by that?

7:23 am  
Blogger J said...

The "belief" quasi-epistemology chat is quite a different matter than logic/analysis. "Felines are mammals; ergo, felines are vertebrates". No problems, and no need to indulge in the belief chat--which quickly becomes a matter of psychology (or guestimates). The validity of arguments has nothing to do with belief, anymore than calculus does. We can point to felines..or integrals (and we will agree on definitions--if we don't its a short conversation). Point to a belief. Pure mentalism as old behaviorists, however quaint, would say.

8:38 pm  
Blogger Anthony said...

>> The story we are playing along with in these discussions is pretty definite about Clark Kent being Superman, and that individual being able to fly.

What story is that? You realize that in the original comic book Superman could not fly, right?

Ed says the reader is always shown Clark Kent "changing from his office suit and glasses to his Superman costume, without glasses". But that's not even true. The scenes show Superman taking off his Clark Kent costume, and revealing the true identity of Superman underneath.

In other words, according to the story, Superman is *not* identical with Clark Kent. Clark Kent is, according to the story, a character played by Superman.

Which sounds incredibly backwards and unintuitive. But that's what we get for trying to gain insight into logic by dealing with fiction (and incredibly unrealistic fiction at that).

4:40 am  

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