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BTK 18: Kripke (1 of 3) Week 5

Kripke,A priori knowledge, necessity, and contingency

Three distinctions!Philosophers used to believe that apriori = necessary.

o Necessary apriori.It is hard to see how empirical observation could berelevant to determining whether a necessary proposition is true (since the

empirical facts are contingent).

o Apriori necessary.If something can be known independently ofempirical observation, then it would be true regardless of the empirical facts.

Among other things, Kripkes aim is to argue that the traditional identification

apriori = necessaryis mistaken.

oIn particular, Kripke will argue that some contingent propositions areapriori, and that some necessary propositions are aposteriori.

Apriori vs. aposteriori. This is an epistemological distinctionbetween how

things are knowable.

o Proposition P is apriori iff it is knowable independently of experience. Bachelors are unmarried males and 2+2=4. An apriori proposition could be known by someone on aposteriori grounds.

o Proposition P is aposteriori iff it is not apriori. I have brown hair and Electrons have negative charge.

Necessary vs. contingent. This is a metaphysical distinctionbetween what

must be true or could have been otherwise.

o Proposition P is necessarily true(false) iff P could not have been false (true). 2+2=4 and Water is H20.

o Proposition P is contingentiff Pis neither necessarily true nor necessarilyfalse.

Bush is president and Kerry is president.Analytic vs. synthetic. This is a semantic distinctionbetween what the

meanings of words might (or might not) make true.

o A truth is analytic iff it is true in virtue of the meanings of its terms. Vixens are female foxes and Bachelors are unmarried males.

o A truth is syntheticiff it is true but not analytic. Water is H20 and Grass is green.

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BTK 18: Kripke (2 of 3) Week 5

Proper names and rigid designationDefinition and reference-fixing. Sometimes the way we describe an object

isnt intended to state the meaning of a name for that object, but rather a way of

picking it out.

o I might describe Tom Cruise as Katie Holmeshusband.o But that is not to give the meaning of the name Tom Cruise.

After all, Tom Cruise might not have been Katie Holmeshusband, but itis impossible that Katie Holmeshusband not be Katie Holmeshusband.

o Tom Cruise is actually Katie Holmeshusband. That lets me use thedescription to fix the reference of Tom Cruise, even if not define it.

How do proper names come to refer what they refer to?

o Causal-historical theory of reference.At some point, an object isbaptizedwith a name, which fixes its reference. Language users pick up

the use of the name, and transmittheir use to others.

Toms parents name him Tomby saying That child in my arms is myson Tom. So do his relatives and friends, and so on

Rigid vs. non-rigid reference. We can refer to Tom Cruise in English in

several ways:

o If we refer to him by using Katie Holmes husband, then we refer to himnon-rigidlysince although this expression actually refers to him, it might

have referred to someone else, like me.

o If we refer to him by using Tom Cruise, then we refer to him rigidlysince,given that we actually use this expression to refer to him, it cannot refer to

anyone else.

Rigid designators.An expression e is a rigid designator iff e refers to the same

object in all possible worlds.

o Tom Cruise is a rigid designator, but Katie Holmeshusband is not.

The contingent apriori Standard meter stick example.

Suppose we take a certain stick S and stipulatively fix the reference of meterby claiming that 1 meter is the length of S.

Then, it is apriorithat S is 1 meter long.

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BTK 18: Kripke (3 of 3) Week 5

After all, 1 meteris a rigid designator the reference of which isstipulatively fixed as the (actual) length of S.

But it is also contingent that S is 1 meter long. After all, 1 meter necessarily refers to the actuallength of S but S

could have been longer or shorter than it actually is.

The necessary aposteriori

Hesperus/Phosphorous example. The ancients thought that the Morning Star, Phosphorous, and the Evening

Star, Hesperus, were two distinct stars. It turns out that they were both the

planet Venus.

It is aposteriori that, necessarily, Hesperus is Phosphorous. After all, it took empirical investigation to discover that.

But if Hesperus and Phosphorous are both rigid designators(Kripkeclaims they are), then it is necessarythat Hesperus is Phosphorous.

After all, if two names are rigid designator, then if they have the samereferents, then they necessarilyhave the same referents.

(1) Suppose a = b.(2) a refers to o in all possible worlds. [Names are rigid](3) b refers to o in all possible worlds. [Names are rigid](4) So a = b iff o = o. [From (1)-(3)](5) Necessarily, o = o. [(1),(4)](6) Therefore, necessarily a = b. [(1),(4)-(5)]