This passage leads us to his second thesis, namely, the excellence of these economic institutions. As we have already remarked, these two ideas of spontaneity and excellence, though confused by Smith, ought to be treated apart. His naturalism and optimism are inseparable, and both of them find expression in the same paragraph. The passage just quoted affords a proof of this. Personal interest not only creates and maintains the economic organism, but at the same time ensures a nation’s progress towards wealth and prosperity. The institutions are not only natural, but are also beneficial. They interest him not merely as objects of scientific curiosity, but also as the instruments of public weal. Herein lies their chief attraction for him, for political economy to him was more of a practical art than a science.[208] But this is hardly emphatic enough. Natural economic institutions are not merely good: they are providential. Divine Providence has endowed man with a desire to better his condition, whence arises the “natural” social organism: so that man, following where this desire leads, is really accomplishing the beneficent designs of God Himself. By pursuing his own interest, man “is in this as in many other cases” (he is writing now of the employment of capital) “led by an invisible hand to promote an end which was no part of his intention.”[209] The Physiocrats could hardly have improved upon that. We can scarcely share in his optimism to-day. But it has played too prominent a _rôle_ in the history of ideas not to detain us for a moment. We must examine the arguments upon which it is based and endeavour to grasp their import. Let us note, in the first place, that every example hitherto deduced with a view to proving the spontaneity of economic institutions at the same time furnishes a demonstration of the beneficial effects of personal interest. Owing to a coincidence by no means fortuitous every institution mentioned by Smith as owing its existence to the prevalence of action of this kind is at the same time favourable to economic progress. Division of labour, the invention of money, and the accumulation of capital are so many natural social facts that also increase wealth. The adaptation of demand and supply, the distribution of money according to the need for a circulating medium, the growth of population according to the demand for it, are so many spontaneous phenomena which ensure the efficient working of economic society. A perusal of Smith’s work leaves us with the impression that these spontaneous institutions must also be the best.