From 1763 to 1765, Hume was invited to attend Lord Hertford in Paris, where he became secretary to the British embassy.  While there he met with Isaac de Pinto  and fell out with Jean-Jacques Rousseau . Hume was sufficiently worried about the damage to his reputation from the quarrel with Rousseau (who is generally believed to have suffered from paranoia ) to have authored an account of the dispute, which he titled, appropriately enough "A concise and genuine account of the dispute between Mr. Hume and Mr. Rousseau."  In 1765, he served as British Chargé d'affaires , writing "despatches to the British Secretary of State".  He wrote of his Paris life, "I really wish often for the plain roughness of The Poker Club of Edinburgh ... to correct and qualify so much lusciousness".  In 1766, upon returning to Britain, Hume encouraged Lord Hertford to invest in a number of slave plantations, acquired by George Colebrooke and others in the Windward Islands .  In 1767, Hume was appointed Under Secretary of State for the Northern Department. Here he wrote that he was given "all the secrets of the Kingdom". In 1769 he returned to James' Court in Edinburgh, and then lived, from 1771 until his death in 1776, at the southwest corner of St. Andrew's Square in Edinburgh's New Town , at what is now 21 Saint David Street.  A popular story, consistent with some historical evidence, suggests the street may have been named after Hume. 
There are reams of literature addressing whether these two definitions are the same and, if not, to which of them Hume gives primacy. Robinson is perhaps the staunchest proponent of the position that the two are nonequivalent, arguing that there is an nonequivalence in meaning and that they fail to capture the same extension. Two objects can be constantly conjoined without our mind determining that one causes the other, and it seems possible that we can be determined that one object causes another without their being constantly conjoined. But if the definitions fail in this way, then it is problematic that Hume maintains that both are adequate definitions of causation. Some scholars have argued for ways of squaring the two definitions (Don Garrett, for instance, argues that the two are equivalent if they are both read objectively or both read subjectively), while others have given reason to think that seeking to fit or eliminate definitions may be a misguided project.