Saul%20Kripke,%20

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Saul Kripke, Identity and Necessity

• Driving question How are contingent identity
  statements possible?
• For example, we take it to be the case that it is
  contingent that the first postmaster of the
  United States is identical with the inventor of
  bifocals (i.e. Benjamin Franklin). (73b)

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An apparent paradox

1. (?x)(?y)(x y) ? (Fx ? Fy) Law of
   substitutivity
2. (?x) ?(x x) Every object is necessarily
   self-identical
3. (?x)(?y)(x y) ? ?(x x) ? ?(x y)
   Substitution for (1)
4. (?x)(?y)((x y) ? ?(x y))

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The paradox with proper names

• It would, therefore, seem that the function of
  names is simply to refer, and not to describe the
  objects so named by such properties as being the
  inventor of bifocals or being the first
  Postmaster General. (74b)
• And so, it would seem that a and b stand for
  names, it would seem that we should be able to
  make the following claim
• (a b ? Fa) ? Fb.

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Identities in science

• Water is H2O.
• Heat is molecular motion.
• Gold has atomic number 79 i.e. is a 79 proton
  kinda thing.
• Kripkes view identities are necessary if true.
  (76b)

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Rigid vs. nonrigid designators

• Please note rigid not ridged!
• Rigid designator a term that designates the
  same object in all possible worlds. (77a)
• What does this mean?
• What does it mean to talk about different
  possible worlds?

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A multiplicity of possible worlds

• Wa W
• 43rd Pres. Loser in 2000
• Bush Bush
• Gore Gore
• 2000 Loser 43rd Pres.

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• Bush and Gore are rigid designators.
• 43rd President and Loser in 2000 are nonrigid
  designators.
• Why? Because they can refer to (designate)
  different things in different possible worlds.
• Kripkes claim is that natural kind terms are
  also rigid designators.
• Whats a natural kind? Water, Tiger, Trout,
  Gold, and so on. Terms that we use to cut
  nature at its joints.

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Analytic, necessary, a priori, certain.

• What do we mean by calling a statement
  necessary? We simply mean that the statement in
  question, first, is true, and, second, that it
  could not have been otherwise. When we say that
  something is contingently true, we mean that,
  though it is in fact the case, it could have been
  otherwise. If we wish to assign this distinction
  to a branch of philosophy, we should assign it to
  metaphysics. To the contrary, there is the
  notion of an a priori truth. An a priori truth
  is supposed to be one which can be known to be
  true independently of all experience. Now, this
  notion, if we were to assign it to a branch of
  philosophy, belongs, not to metaphysics, but to
  epistemology. (79b)
• Kripke continues
• Now I hold, as a matter of fact, that neither
  class of statements is contained in the other.
  But all we need to talk about here is this Is
  everything that is necessary knowable a priori or
  know a priori? (80a)

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The problem of essentialism.

• What are the properties that are essential to
  x?Kripkes example of the lectern. Could it
  have been made of ice? (80b)
• If essentialism is correct, then we will have
  necessary a posteriori truths.
• p ? ?p
• p______
• ? ?p
• E.g. if the lectern were not made of ice, then
  it was necessarily not made of ice.

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• Kripke shows that identity is, in cases of names
  and theoretical identifications, necessary.
• E.g. Cicero is Tully
• Mark Twain is Samuel Clemens
• Heat is molecular motion
• Water is H2O
• But not
• Bush is the 43rd President
• Why? Because there is a possible world in which
  Gore was elected the 43rd President.

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A sketch of Kripkes argument

• Water is H2O in the actual world.
• If water is H2O in the actual world, then water
  is H2O in every possible world.
• Therefore, water is H2O in every possible world.
• If something holds in every possible world, then
  it is necessarily true.
• Therefore, it is necessarily true that water is
  H2O.
• The argument follows from truth of premises (1),
  (2), and (4). (3) follows from (1) and (2) (5)
  follows from (3) and (4).