Dictionary of Difficult Words - reductio ad absurdum
reductio ad absurdum
n.n. 'reduction to absurdity'; proving a proposition by showing that its opposite is absurd; disproving a proposition by deducing from it an absurd conclusion; such conclusion.
Although often coloured yellow, the island is intended to be copper, reflecting the country's name, ‘Copper Island’. Effective date: c. September 1960.