Combining Philosophers

Ideas for Melvin Fitting, Chris Daly and Bernard Linsky

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5 ideas

5. Theory of Logic / A. Overview of Logic / 8. Logic of Mathematics
11026 Classical logic is deliberately extensional, in order to model mathematics [Fitting]
     Full Idea: Mathematics is typically extensional throughout (we write 3+2=2+3 despite the two terms having different meanings). ..Classical first-order logic is extensional by design since it primarily evolved to model the reasoning of mathematics.
     From: Melvin Fitting (Intensional Logic [2007], §1)
5. Theory of Logic / F. Referring in Logic / 2. Descriptions / b. Definite descriptions
18774 Definite descriptions, unlike proper names, have a logical structure [Linsky,B]
     Full Idea: Definite descriptions seem to have a logical structure in a way that proper names do not.
     From: Bernard Linsky (Quantification and Descriptions [2014], 1.1.1)
     A reaction: Thus descriptions have implications which plain names do not.
5. Theory of Logic / F. Referring in Logic / 2. Descriptions / c. Theory of definite descriptions
21727 Definite descriptions theory eliminates the King of France, but not the Queen of England [Linsky,B]
     Full Idea: The theory of definite descriptions may eliminate apparent commitment to such entities as the present King of France, but certainly not to the present Queen of England.
     From: Bernard Linsky (Russell's Metaphysical Logic [1999], 7.3)
5. Theory of Logic / F. Referring in Logic / 3. Property (λ-) Abstraction
11028 λ-abstraction disambiguates the scope of modal operators [Fitting]
     Full Idea: λ-abstraction can be used to abstract and disambiguate a predicate. De re is [λx◊P(x)](f) - f has the possible-P property - and de dicto is ◊[λxP(x)](f) - possibly f has the P-property. Also applies to □.
     From: Melvin Fitting (Intensional Logic [2007], §3.3)
     A reaction: Compare the Barcan formula. Originated with Church in the 1930s, and Carnap 1947, but revived by Stalnaker and Thomason 1968. Because it refers to the predicate, it has a role in intensional versions of logic, especially modal logic.
5. Theory of Logic / I. Semantics of Logic / 5. Extensionalism
21719 Extensionalism means what is true of a function is true of coextensive functions [Linsky,B]
     Full Idea: With the principle of extensionality anything true of one propositional functions will be true of every coextensive one.
     From: Bernard Linsky (Russell's Metaphysical Logic [1999], 6.3)