Combining Philosophers

Ideas for Engelbretsen,G/Sayward,C, Peter Koellner and Michael Dummett

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3 ideas

2. Reason / A. Nature of Reason / 5. Objectivity
What matters in mathematics is its objectivity, not the existence of the objects [Dummett]
     Full Idea: As Kreisel has remarked, what is important is not the existence of mathematical objects, but the objectivity of mathematical statements.
     From: Michael Dummett (Frege Philosophy of Language (2nd ed) [1973], Ch.14)
     A reaction: [see Maddy 2011:115 for the history of this idea] It seems rather unclear where Frege stands on objectivity. Maddy embraces it, following up this idea, and Tyler Burge's fat book on objectivity.
2. Reason / D. Definition / 7. Contextual Definition
A contextual definition permits the elimination of the expression by a substitution [Dummett]
     Full Idea: The standard sense of a 'contextual definition' permits the eliminating of the defined expression, by transforming any sentence containing it into an equivalent one not containing it.
     From: Michael Dummett (Frege philosophy of mathematics [1991], Ch.11)
     A reaction: So the whole definition might be eliminated by a single word, which is not equivalent to the target word, which is embedded in the original expression. Clearly contextual definitions have some problems
2. Reason / E. Argument / 6. Conclusive Proof
A successful proof requires recognition of truth at every step [Dummett]
     Full Idea: For a demonstration to be cogent it is necessary that the passage from step to step involve a recognition of truth at each line.
     From: Michael Dummett (The Justification of Deduction [1973], p.313)
     A reaction: Dummett cited Quine (esp. 1970) as having an almost entirely syntactic view of logic. Rumfitt points out that logic can move validly from one falsehood to another. Even a 'proof' might detour into falsehood, but it would not be a 'canonical' proof!