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Single Idea 8179

[from 'Thought and Reality' by Michael Dummett, in 5. Theory of Logic / D. Assumptions for Logic / 2. Excluded Middle ]

Full Idea

The law of excluded middle is the reflection, within logic, of the principle of bivalence. It states that 'For any statement A, the statement 'A or not-A' is true'.

Clarification

Bivalence says sentences can only be 'true' or 'false'

Gist of Idea

The law of excluded middle is the logical reflection of the principle of bivalence

Source

Michael Dummett (Thought and Reality [1997], 5)

Book Reference

Dummett,Michael: 'Thought and Reality (Gifford Lectures)' [OUP 2006], p.62


A Reaction

True-or-not-true is an easier condition to fulfil than true-or-false. The second says that 'false' is the only alternative, but the first allows other alternatives to 'true' (such as 'undecidable'). It is hard to challenge excluded middle. Somewhat true?