The text summarizes the relevant modal pairings as:
Necessary ↔ general possible
Permanent ↔ general absolute/actual
General conditional ↔ temporal possible
General customary ↔ temporal absolute
These are not mere verbal substitutions. Quality, quantity and modal scope must all be matched correctly for each pair.
To negate a modal claim, determine precisely what would make the original claim false, and express that failure at the proper scope.
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Contradiction: Definition, Conditions and Application to Propositions
The text summarizes the relevant modal pairings as:
Necessary ↔ general possible
Permanent ↔ general absolute/actual
General conditional ↔ temporal possible
General customary ↔ temporal absolute
These are not mere verbal substitutions. Quality, quantity and modal scope must all be matched correctly for each pair.
To negate a modal claim, determine precisely what would make the original claim false, and express that failure at the proper scope.