Dugald Stewart further states, on the authority of gentlemen who were students in the moral philosophy class at Glasgow in 1752 or 1753, that Smith delivered so early as that lectures containing the fundamental principles of the _Wealth of Nations_; and in 1755--the year Cantillon's _Essai_ first saw the light, and the year before Quesnay published his first economic writing--Smith was not only expounding his system of natural liberty to his students, but publicly asserting his claim to the authorship of that system in a Glasgow Economic Society--perhaps the first economic club established anywhere. The paper in which Smith vindicates this claim came somehow into the possession of Dugald Stewart, and so escaped the fire to which Smith committed all his other papers before his death, but it is believed to have been destroyed by Stewart's son, very possibly after his father's directions. For Stewart thought it would be improper to publish the complete manuscript, because it would revive personal differences which had better remain in oblivion, and consequently our knowledge of its contents is confined to the few sentences which he has thought right to quote as a valuable evidence of the progress of Smith's political ideas at that very early period. It will be observed that, as far as we can collect from so small a fragment of his discourse, he presents the doctrine of natural liberty in a more extreme form than it came to wear after twenty years more of thought in the _Wealth of Nations_. Stewart says that many of the most important opinions in the _Wealth of Nations_ are detailed in this document, but he cites only the following:--