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Ideas for 'Thinking About Mathematics', 'Material Beings' and 'Letters'

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2 ideas

5. Theory of Logic / D. Assumptions for Logic / 2. Excluded Middle
The 'Law' of Excluded Middle needs all propositions to be definitely true or definitely false [Inwagen]
     Full Idea: I think the validity of the 'Law' of Excluded Middle depends on the assumption that every proposition is definitely true or definitely false.
     From: Peter van Inwagen (Material Beings [1990], 18)
     A reaction: I think this is confused. He cites vagueness as the problem, but that is a problem for Bivalence. If excluded middle is read as 'true or not-true', that leaves the meaning of 'not-true' open, and never mentions the bivalent 'false'.
Intuitionists deny excluded middle, because it is committed to transcendent truth or objects [Shapiro]
     Full Idea: Intuitionists in mathematics deny excluded middle, because it is symptomatic of faith in the transcendent existence of mathematical objects and/or the truth of mathematical statements.
     From: Stewart Shapiro (Thinking About Mathematics [2000], 1.2)
     A reaction: There are other problems with excluded middle, such as vagueness, but on the whole I, as a card-carrying 'realist', am committed to the law of excluded middle.