Thou Shalt Preserve the Unities of Time and Place

Thou shalt preserve the unities of time and place, as commended by the High Priest Nicolas Boileau, placing thyself, in imagination, in one time and one place, and distinguishing all others to which thou mayest refer by a proper use of tenses and other forms of speech devised for this purpose; for unless we exploit the distinction between past and pluperfect tenses, and between imperfect and future conditional, we cannot attain perfect limpidity of style and argument.

HUGH TREVOR-ROPER