Verified answer

This quotation from Oscar Wilde's "The Importance of Being Earnest" is an epigram, defined thus:

An epigram is a brief, interesting, memorable, and sometimes surprising or satirical statement. Derived from the Greek: ἐπίγραμμα epigramma "inscription" from ἐπιγράφειν epigraphein "to write on – inscribe", this literary device has been employed for over two millennia.

http://en.wikipedia.org/wiki/Epigram

Wilde was a master of epigrams and the following book acknowledges "in grave importance, style, not sincerity is the vital thing" as one of the most significant epigrams in Wilde's greatest play, pointing as it does to the drama's underlying meaning:

http://books.google.co.uk/books?id=7hq8N3NtmhgC&pg...