Lecture 7

Dr. Ron Mallon                                                            Philosophy of Cognitive Science

 

I.  ANNOUNCEMENT to philosophy majors and those taking many philosophy classes:

Please consider turning in a picture of yourself to Vivian Chu in the philosophy department.

 

II.  Semantic Parallels

Meaningfulness parallels

     Syntactic

            Productivity:  Infinite number of sentences/infinite number of thoughts

            Systematicity: Systematic relationships among thoughts.

III.  Processing Argument:

            Cannot strategize without representations

            Cannot learn without representations

           

IV.  I am now going to consider some a priori considerations that Fodor thinks favor acceptance of the language of thought hypothesis (from ‘Propositional Attitudes’).

 

1.  Common sense belief attribution progresses by relating a person to a proposition.  E.g. we say: “Mary believes that global warming is a serious problem.”  We relate Mary to the proposition that global warming is a serious problem.  And the character of her relation is one of believing. 

 

The language of thought hypothesis (LOTH) is, in effect, the hypothesis that we should take Mary to be literally related to a sentence in a language of thought inside of her head.  Hence, the language of thought hypothesis preserves the relationship that commonsense suggests is there.

 

2.  Opacity:  A theory of propositional attitudes should account for the opacity of belief attributions.

 

Opacity arises in ‘opaque’ contexts - contexts in which there is a failure of substitution of co-referring terms salve veritate (or ‘preserving truth’).

 

Let me explain.  Consider the sentence:

(1) Superman can fly.                   

This sentece is (let us say) true.  Now consider,

            (2)  Superman is Clark Kent.

The ‘is’ in (2) is the ‘is’ of identity.  Superman and Clark Kent are the same person.  From this, it follows that,

            (3) Clark Kent can fly.

Notice that (3) is very similar to (1).  The sentences are the same except that the term ‘Superman’ in (1) has been replaced by the term ‘Clark Kent’ in (3).  Because ‘Superman’ and ‘Clark Kent’ pick out the same person, we say they are ‘co-referring’.  And in many sentences, we can substitute co-referring terms in a way that ‘preserves’ truth.  That is, if the original sentence is true, the new sentence formed by the substitution will also be true.  Such contexts are called ‘transparent’.

 

     However, other contexts are called opaque.  Two examples are contexts of utterance, and attributions of mental states.  In such contexts, substitution fails to preserve truth.  That is, we can substitute co-referring terms for terms in a true sentence and get a false sentence.  E.g.

 

Lois Lane said, “Superman can fly.”                  True.

Lois said, “Clark Kent can fly.”                        False.

 

Lois Lane believes that Superman can fly.        True    

Lois Lane believes that Clark Kent can fly.        False.

 

Fodor thinks that a theory of prepositional attitudes should explain such opacity.  LOTH does this by relating persons to physical objects.  To say a person is related to one internal symbol (or object type) is not to say they are related to a second - even if the two types have the same referent.  Hence, substitution fails.

 

3.  Aristotle’s Condition

     A third consideration Fodor thinks should weigh in our assessment of a theory of prepositional attitudes is whether the theory allows us to understand the operation of practical reason.

 

Aristotle thought that practical reason proceeded by practical syllogism.  For example,

(1) Joe wants to eat lunch.

(2) Joe believes that by going to the canteen, he will be able to eat lunch.

(3) Therefore, Joe intends to go to the canteen.

 

The point is simply this: for such practical reason to operate successfully, the terms in the various lines (e.g. terms like ‘lunch’) must have the same representational content from line to line.  If what Joe’s belief is about is not the same as what his desire is about, then there will be no reason for him to develop an intention to act.

 

V.  Fodor contrasts his view with an alternative view that solves many of the same problems, one that he calls: “Carnap’s Theory.”

 

This theory (reconstrued) holds that having a belief is being in some or another relationship to an utterance of a sentence in a natural language.

 

Fodor thinks there are a number of problems with this approach.  The two I will focus on are these:

 

1.  It’s possible for “Joe believes it is raining” to be true even if Joe speaks no English.

 

This seems like a problem on Carnap’s theory.  Why would there be a true statement relating a non-English speaker to terms in English?

 

2.  It seems like we need a language of thought in order to frame beliefs about natural language as we learn it.  E.g. THE WORD ‘cat’ MEANS CAT (where I have used capitalization to indicate the language of thought).  If there is no language of thought, how could we learn a first language?