It was just as the 1914 War burst on me that I made the discovery that 'legends' depend on the language to which they belong; but a living language depends equally on the 'legends' which it conveys by tradition. … Volapuk, Esperanto, Ido, Novial, &c &c are dead, far deader than ancient unused languages, because their authors never invented any Esperanto legends...
No. 180: To a Mr. Thompson (1956) - The Letters of J. R. R. Tolkien (1981)