A Treatise of Human Nature

London is the true first; Hume wrote in English and there is no competing foreign or original-language edition, so the whole precedence question is the Noon/Longman sequence itself. The census claim is confirmed: vols. I-II John Noon 1739, vol. III Thomas Longman 1740. Because the third volume appeared roughly eighteen months later from a different house, the two Noon volumes are very often found alone - a two-volume set is not a complete first edition, and complete three-volume sets are genuinely rare. Sources consulted disagree on the month of vol. III (October 1740 vs. 5 November 1740), so only the year 1740 should be relied on.