A third and by far the most important intellectual influence which tended toward the destruction of the system of regulation was the development of a consistent body of economic teaching, which claimed to have discovered natural laws showing the futility and injuriousness of any such attempts. Adam Smith's _Wealth of Nations_ was published in 1776, the year of the invention of Crompton's mule, and in the decade when enclosures were more rapid than at any other time, except in the middle years of the Napoleonic wars. This was, therefore, one of the earliest, as it was far the most influential, of a series of books which represent the changes in ideas correlative to the changes in actual life already described. It has been described as having for its main object "to demonstrate that the most effectual plan for advancing a people to greatness is to maintain that order of things which nature has pointed out, by allowing every man, as long as he observes the rules of justice, to pursue his own interests in his own way, and to bring both his industry and his capital into the freest competition with those of his fellow-citizens." But the most distinct influence exercised by the writings of Adam Smith and his successors was not so much in pointing out that it was unjust or unwise to interfere with men's natural liberty in the pursuit of their interests, as in showing, as it was believed, that there were natural laws which made all interference incapable of reaching the ends it aimed at. A series of works were published in the latter years of the eighteenth and the early years of the nineteenth century by Malthus, Ricardo, Macculloch, James Mill, and others, in which principles were enunciated and laws formulated which were believed to explain why all interference with free competition was useless or worse. Not only was the whole subject of economic relations clarified, much that had been regarded as wise brought into doubt, and much that had been only doubted shown to be absurd, but the attainment of many objects previously sought for was, apparently, shown to be impossible, and to lie outside of the realm of human control.