In addition to this, Smith has been successful in borrowing from his predecessors all their more important ideas and welding them into a more general system. He superseded them because he rendered their work useless. A true social and economic philosophy was substituted for their fragmentary studies, and an entirely new value given to their contributions. Taken out of their isolation, they help to illustrate his general theory, becoming themselves illuminated in the process. Like most great writers, Smith knows how to borrow without impairing his originality. Over a hundred authors are quoted in his book, but he does not always acknowledge them. The names of some of the writers who exercised such influence over him, and opened up the path which he afterwards followed, deserve more than a passing reference. The first place among these belongs, perhaps, to Hutcheson, Smith’s predecessor in the chair of Moral Philosophy at Glasgow. The divisions of the subject are almost identical with those given by Hutcheson, and many of Smith’s best known theories can be traced in the _System of Moral Philosophy_ published by Hutcheson in 1755, but which we know was written long before. Hutcheson laid great stress upon the supreme importance of division of labour, and his views on such questions as the origin and variations in the value of money and the possibility of corn or labour affording a more stable standard of value closely resemble those of the _Wealth of Nations_. David Hume is a near second. Smith refers to him as “by far the most illustrious philosopher and historian of the present age,”[127] and from 1752 onward they were the closest of friends. Hume was already the author of some essays on economic questions, the most important among them dealing with money, foreign trade, the rate of interest, etc. These, along with several other writings, were published in the _Political Discourses_ in 1752. Hume’s examination of these problems displays his original penetrative thought, and there is evident the profundity and lucidity of treatment characteristic of all his writings. The absurdity of the Mercantile policy and of interfering with the natural tendency of money to adapt itself to the needs of each community, the sophistry of the balance of trade theory, and the impious consequences resulting from commercial jealousy among nations are exposed with admirable force in these essays. No doubt the essays left a great impression upon Smith. He quoted them in his lectures at Glasgow, and Hume consulted him before bringing out a second edition. It is true that Smith eventually became the stauncher Liberal of the two. Hume, in his essay on the _Balance of Trade_, recognized the legitimacy of certain protective rights which Smith wished removed altogether. Still it was to Hume that Smith owed his conversion to the Liberal faith.