indirect proof

noun

an argument for a proposition that shows its negation to be incompatible with a previously accepted or established premise.

indirect proof

logic maths proof of a conclusion by showing its negation to be self-contradictory; reductio ad absurdum Compare direct

The considerations just adduced imply the immortality of the soul, to which they lend indirect proof.

He really gives an indirect proof of the reverse theory, as E. Dubois-Reymond rightly observed in his brilliant memorial speech.

At present I am content with the indirect proof that the existence of such a standard is necessary to the existence of the arts.

This appears to us to be an indirect proof that the half lines in Virgil are often complete as they stand.

But an indirect proof must reduce to absurdity all the possibilities except one, in order to be a proof.

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