Consistency (Meta) Math Example 3

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Example 3

easy
A proof assumes both 'nn is even' and 'nn is odd'. Is this assumption consistent? What follows?

Solution

  1. 1
    A number cannot be both even and odd simultaneously — the assumptions are inconsistent.
  2. 2
    From a contradiction, any statement can be derived (ex falso quodlibet). The proof is therefore invalid unless this inconsistency was introduced deliberately as a proof by contradiction.

Answer

InconsistentĀ assumption — theĀ proofĀ containsĀ anĀ errorĀ (orĀ isĀ attemptingĀ aĀ contradiction)\text{Inconsistent assumption — the proof contains an error (or is attempting a contradiction)}
Inconsistent assumptions invalidate any argument built on them. In mathematics, the only legitimate use of contradictory assumptions is in proof by contradiction, where they are introduced to be refuted.

About Consistency (Meta)

The property of a set of mathematical statements having no internal contradictions — all statements can be simultaneously true within the same system.

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