Could I Be a Brain-Body Composite?

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8 responses to “Could I Be a Brain-Body Composite?”

1. 

   peterlupu

   May 9, 2009

   Bill,
   A minor comment: in (a) you need to add the provision that ‘x’ and ‘y’ are rigid and then in (b) you need to show that the pronoun ‘I’ is rigid and that whatever term used to refer to the brain in the right hand side of the identity is also rigid. For instance, if we substitute non-rigid description for ‘x’ and ‘y’ in (a), then it will be false.
   (Note: I say non-rigid descriptions because some in the literature maintain that there are rigid descriptions. I am not confident that there are, but just in case, I added this proviso).
   peter

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2. 

   Bill Vallicella

   May 9, 2009

   Peter,
   But are ‘x’ and ‘y’ ever used as variables whose substituends are descriptions? The substituends of individual variables such as ‘x’ and ‘y’ are standardly taken to be names, where names are rigid designators. Isn’t that right? But you are right that if descriptions *were* substituted for ‘x’ and ‘y,’ then (1) could come out false, e.g., this is false: ‘If the fastest runner in Jerome = the skinniest woman in Jerome, then necessarily the fastest runner in Jerome = the skinniest woman in Jerome.’
   How could ‘I’ be nonrigid? When a person tokens ‘I,’ he refers to the same individual in every possible world in which that individual exists. ‘The best chessplayer in Gold Canyon’ refers to me but nonrigidly. I fail to see how ‘I’ used by me could fail to refer to me in every world in which I exist.
   Same with ‘my brain’ which can be analyzed in terms of the first person singular pronoun.
   Are there rigid descriptions? I should think so. How about ‘that than which no greater can be conceived’?

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3. 

   Bill Vallicella

   May 9, 2009

   Addendum: I’m not saying that it is standard doctrine that names are rigid designators, but that it is standard doctrine that the substituends of individual variables such as ‘x’ and ‘y’ are names. Or are there philosophers whose notation allows a description to be a substituend for ‘x’?

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4. 

   peterlupu

   May 9, 2009

   Bill,
   I certainly think you are right about ‘I’ being rigid. Regarding ‘my brain’, that is somewhat less obvious, but I think we can grant that without much risk.
   Typically, the substituents of individual variables are terms which designate an individual object including names or descriptions; hence, in general, the provision that the substituents should be rigid is always added.
   peter

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5. 

   Bill Vallicella

   May 10, 2009

   Peter,
   You may be right as to your main point, but I wonder if you have a passage in Kripke or somebody else to which you can refer me.

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6. 

   peterlupu

   May 10, 2009

   Bill,
   The principal reference is “Naming and Necessity”, but I do not remember page number. In Standford Encyclopedia of Philosophy there is an article about rigid designators (just type in ‘rigid designators’) and the article will be the first one that comes up. In the first section the author states the point I have made.
   Intuitively the reason rigid designators turn an identity statement necessary true, if it is true, is because a rigid designator refers to the very same object to which it actually refers in all possible world in which the object exists; so if an identity statement flanked by two rigid terms is true in the actual world, then the terms will refer to the same object in all other possible worlds in which it exists and thus the identity statement is going to be true in all of these worlds. The reason the same does not hold for non-rigid descriptions is because the reference of such a description is liable to vary from world to world and therefore the object picked out by a description is not the same throughout the worlds.
   peter

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7. 

   Bill Vallicella

   May 10, 2009

   Peter,
   I read the first section of the SEP article, but I don’t see that it addresses the question we are discussing at all. Here again is
   (a): a. If x = y, then necessarily x = y. (Principle of the Necessity of Identity).
   You say I have to add that ‘x’ and ‘y’ are rigid. I claim that that
   addition is not necessary, because ‘x,’ ‘y’,’z’ are individual variables (not individual constants, and not property variables)whose SUBSTITUENDS (not to be confused with VALUES) are understood to be logically proper names, not descriptions.

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8. 

   peterlupu

   May 10, 2009

   Bill,
   If we grant that names are rigid and that the substituends of the variables are to be only names, then you of course get the result that any instance of (a) will have only rigid designators flanking the identity sign. o then we agree on the central issues.
   peter

   Reply