The Wealth of Nations (1776). But, on the other hand, the fact that both works were originally parts of one and the same course of lectures does not harmonize with this view. Moreover the fact has been overlooked, that in his political economy Smith assumes the attitude of an "impartial witness" of industrial life: his demand for unconditional liberty in commerce and industry rests upon the principle that this is the only way in which capacity can be properly developed and the best methods and instruments of production and of trading be discovered. It frequently happens that the individual serves the community best when he is most concerned about his own interests; he, at the same time, serves a purpose which he has not proposed as if guided by an unseen hand. Sympathy with human life in every phase forms the basis of Smith's political economy; it covers the effort of laborers to secure better wages, as well as the effort of employers to increase production. His ethics is therefore in internal harmony with his economics. It is admitted, as a matter of course, that he did not fully appreciate the social problem in its entire scope. His contention was directed against the trusteeship of the reactionary governments, and his optimism led him to expect a large measure of social harmony, even a harmony between ethics and economics, if we should only permit evolution to have free course.
The association of ideas had a profound influence on Hume's theory of knowledge. The physician, David Hartley(1705-1757), supplemented his theory on this point. He endeavored to explain all the higher mental phenomena by means of the association of simple sensations and ideas. According to Hartley, the laws of association are the highest spiritual laws of nature
