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assumption (in a proof)

A sentence supposed for the sake of argument at the start of a subproof.

An assumption is a sentence written at the head of a subproof without justification from earlier lines, marked AS. Everything inside that subproof depends on it, and it is discharged when the subproof closes.

Examples

  • To prove P → Q, assume P and try to reach Q.

See also

subproof discharge
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