A Secret Vice: Tolkien on Invented Languages
J. R. R. Tolkien, Dimitra Fimi et Andrew Higgins2016

A Secret Vice is the title of a lecture written by J. R. R. Tolkien in 1931, given at a conference. Some twenty years later, Tolkien revised the manuscript for a second presentation.

It deals with constructed languages in general, and the relation of a mythology to its language. Tolkien contrasts international auxiliary languages with artistic languages constructed for aesthetic pleasure. Tolkien also discusses phonaesthetics, citing Greek, Finnish, and Welsh as examples of "languages which have a very characteristic and in their different ways beautiful word-form".

Tolkien's opinion of the relation of mythology and language is reflected in examples cited in Quenya and Noldorin, the predecessors of Quenya and Sindarin. The essay contains three Quenya poems, Oilima Markirya ("The Last Ark"), Nieninque, and Earendel, as well as an eight-line passage in Noldorin.