Formulations close to Gell-Mann's are used in T. H. White 's 1958 (not 1938–39) version of The Once and Future King, Jack Parsons 's 1948 essay "Freedom is a Two-Edged Sword", and Robert Heinlein 's 1940 short story "Coventry". They differ in details such as the order of the words "forbidden" and "compulsory", and Gell-Mann's footnote uses the words in both orders, although only one of these orders captures his precise logical meaning. The phrase, and variations on it, appear to have been common in this period, and probably trace back to an older legal principle, that everything which is not forbidden is allowed. Since White did not use the phrase in any published work until two years after Gell-Mann's paper, White cannot have been Gell-Mann's source. It is likely that writers such as White, Heinlein, and Gell-Mann were all simply making use of a phrase that was a part of popular culture at the time.