During the time Mr. Smith was thus successfully engaged in his academical labours, he was gradually laying the foundation of a more extensive reputation. In the year 1759, he published his 'Theory of Moral Sentiments, or An Essay towards an Analysis of the Principles by which Men naturally judge concerning the Conduct and Character, first of their Neighbours, and afterwards of Themselves.' This work was founded on the second division of his lectures, and was divided into six parts:--The propriety of action: Merit and demerit, or the objects of reward and punishment: The foundation of our judgments concerning our own sentiments and conduct, and of the sense of duty: The effect of utility upon the sentiment of approbation: The influence of custom and fashion upon the sentiments of moral approbation and disapprobation: And, lastly, The character of virtue. To these were added, a brief view of the different systems of ancient and modern philosophy, which is universally acknowledged to be the most candid and luminous that has yet appeared. This Essay soon attracted a great share of the public attention, by the ingenuity of the reasonings, and the perspicuity with which they were displayed. The principle on which it is founded may be said to be, That the primary objects of our moral perceptions are the actions of other men; and that our moral judgments, with respect to our own conduct, are only applications to ourselves of decisions which we have already passed on the conduct of others. With this doctrine the author thinks all the most celebrated theories of morality coincide in part, and from some partial view of it he apprehends they are all derived. To the same work was subjoined a short treatise on the first formation of language, and considerations on the different genius of those which were original and compounded. The Theory of Moral Sentiments, immediately on its publication, procured a splendid reputation to the author, and led to a change in his situation in life, that was to him no less pleasing in itself, than gratifying from the means by which it was brought about. But the following lively letter to him, at that time, from his friend Mr. Hume, dated London, 12th April, 1759, will best show the manner in which this work was received, and the influence which it had in deciding on the future life of its author:--