A Test of Lucidity

Adam Sisman, An Honourable Englishman (New York: Random House, 2010), pp. 61-62:

Hugh [Trevor-Roper] employed [Alfred Jules] Ayer's categories as a purgative for his prose, rejecting rhetoric, slovenly language, ambiguity or emotive obscurity, and aspiring to limpidity and austerity of style. It became one of his cardinal rules that no sentence of his should have to be read twice in order to be understood. No concept was too difficult to be expressed clearly. A useful test of lucidity was to translate a phrase from English into Latin; the necessary effort of understanding revealed any non-sense, tautology or ambiguity.