1.  The background.

    “Contingent identity.”

    Black's objection.

    Black's descendants:  Kripke, W.D. Hart, Stephen White, David Lewis, George Bealer, and most recently...
 

2.  Frank Jackson and Dave Chalmers.

    What's distinctive here is the militant apriorism.  It is retro.  It is evil.

    Chalmers' simple version:

    (1)  If materialism is true, then every fact admits of reductive explanation in physical terms.

“Reductive explanation” is “explanation wholly in terms of simpler entities.”

    (2)  Reductive explanation of B-facts in terms of A-facts requires the logical supervenience of B-facts on A-facts.

“Logical supervenience” is supervenience in virtue of linguistic meaning, hence a priori; it requires in-principle deducibility, viz., derivability in some logical calculus given analytic definitions.

    (3)  There are phenomenal facts (e.g., facts of what it's like to experience such-and-such a sensation) that do not logically supervene on any physical facts.

 \  (4)  There are phenomenal facts that do not admit of reductive explanation in physical terms.   [2,3]

 \  (5)  Materialism is not true.   [1,4]   QED

3.  Arguments for (2).

    (A)  Direct appeal to conceivability.

    (B)  Otherwise the supervenience would be “an impenetrable mystery.” (Jackson)

    (C)  Otherwise “there will always be a further unanswered question.”

    (D)  All the uncontentious B-facts, considered category by category, do logically supervene on microphysics.
 

4.  Three types of B-statement

        · Directly defined in microphysical terms.

        · Analytically derivable from microphysical statements, through functional definitions.

        · Derivable through rigidified reference-fixers, after empirical discovery.
 

5.  Sample derivation of third type:

        .
        .
        .

    A 30.48-cm-high subregion of [the attic] is occupied by H2O.

 \  The attic has a foot of H2O in it.

    H2O  =  the actual occupant of the “water” role.   [Established empirically, but is derivable from microphysics via functional definition of the role description]

    The actual occupant of the “water” role  =  water.   [Contingent but known a priori]

 \  The attic has a foot of water in it.   [Substituting identicals]   QED

6.  Evans (1979):

    “Let us use `Julius’ to refer to whoever [actually] invented the zip.”
    Then, “Julius invented the zip” is known a priori, or rather, “(If anyone uniquely invented the zip) Julius invented the zip” is.

    “(If there is one and only one actual F) the actual F is the F” is always true, and known a priori.

    “(If there is a unique occupant of the `K’ role) the actual occupant of the `K’ role is K” likewise seems always true, and known a priori.

    Other a priori truths generated by the mechanisms of reference:

    “I am here now”; “I am speaking”; “Dave (assuming he exists) is called `Dave’”; “Water (if any) is called `Water’”; “If `Dave’ refers, it refers to Dave”; “If `water’ refers it refers to water.”   --All are contingent a priori.
 

7.  First objection to the simple version:  Premise (1) is not obvious.

Perspectival facts.
 

8.  Second objection:  Premise (2) seems crazy.

    --Of course, Jackson and Chalmers have defended (2).

    Rebuttal to (A):  This is just the supervenience or necessitation intuition, not a linguistic intuition.  (Also, Block and Stalnaker counterexamples.)

    Rebuttal to (B):  The supervenience needs no further explanation than the constitution claim; identities don't call for explanation even when they are a posteriori.

    Rebuttal to (C):  (i) By this standard, there probably has never been an actual reductive explanation, and almost as probably never will be.
      (ii) See the rebuttal to (B); the constitution claim cannot itself be explained; there is a gap, but not a mystery.

    Rebuttal to (D):  (i) There are categories of B-fact for which logical supervenience clearly fails.
      (ii) There is no reason to think that reduction via analytical functional definitions ever happens or is even possible.
      (iii) In the crucial case of a posteriori identities, I shall argue that Jackson-Chalmers derivations are fallacious.
 

9.  Objections to J-C derivations.

    1.  Why think that a kind-term has a public role-stereotype?  Reference-fixers are at best idiosyncratic, usually private to speakers, and transitory even for individual speakers.  It's most unlikely that there is any “`water’ role.”

    2.  A J-C derivation requires a reduction via analytical functional definitions (e.g., of the “`water’ role” and of each of its sub-roles.  But as before, there is no reason to think that such reductions are available.

    3.  The key premise in a J-C derivation (e.g., “The actual occupant of the `water’ role  =  water”) is not in fact known a priori.  The claim that it is known a priori rests on a use-mention fallacy.  Viz.: Referential a prioritude does not survive disquotation:

I do not know a priori that Julius invented the zip, or even that if anyone uniquely did, he did; you do not know a priori that I am here now; we do not know a priori that Dave is called “Dave.”  Similarly, we do not know a priori that the actual occupant of the “water” role =  water (i.e., H2O).

    Without J-C derivations, Jackson's and Chalmers' simple argument collapses entirely; (2) is still crazy.

10.  But suppose:

    Suppose the J-C derivations were sound.  (I.e., ignore my three objections.)  Then why might not a parallel derivation work for a phenomenal concept?

    Choose any plausible public reference-fixer for the type of sensation I am having; use an Armstrong-Lewis-style role description.  But rigidify it using “actual”; then use it in a J-C premise. E.g., “The actual occupant of the `stinging pain’ role  =  stinging pain.”

    (Chalmers does argue that phenomenal concepts are not analytically role concepts of any kind.  I agree.)

11.  Chalmers' 2-D terminology.

    “Secondary intension”  = intension, i.e., a function from worlds to the term's referents in those worlds.  The intension of “water” picks out H2O at every world.

    “Primary intension”  =  a function that picks out, at a world, the referent the term would have there were it used there according to the (roughly) Kaplanian character it has here.  The primary intension of “water” picks out, at every world, whatever occupies the “water” role at that world.

    A parallel distinction for whole sentences:  A given sentence expresses a “secondary proposition,” i.e., the proposition it would normally be taken to express, and a “primary proposition,” which is the proposition the sentence would express at a world in a context if used there according to the (roughly) Kaplanian character it has here.

    In a Kripkean identity, the primary proposition is contingent.
 

12.  Chalmers’ 2-D argument.

    “1” and “2” indicate primary and secondary propositions respectively; TP is the totality of physical fact, and Q is a phenomenal proposition.

        (1)  It is 1-conceivable that: TP but not Q.

      \ (2)  It is 1-contingent that: if TP then Q.   [1, definitions]

        (3)  A phenomenal term’s 1-intension coincides with its 2-intension.

      \ (4)  It is 2-contingent that: if TP then Q.   [Substituting the conditional’s 2-intension for its 1-intension in 2]

        (5)  Materialism requires that for any sentence S, it is 2-necessary that: if TP then S.

      \ (6)  Materialism is not true.   [4,5]   QED