It has been remarked by Sir James Mackintosh, that there are four great works, in four distinct departments of knowledge, which have more visibly and extensively influenced opinion than any other productions of the human intellect. The first of these is the _Treatise on the Law of War and Peace_, by Grotius. It appeared about two centuries ago; and from that period downwards, international law became a solid fact, which all civilised countries have recognised, and which even the French Convention, during the Reign of Terror, dared, in its madness, to outrage but for a moment. The second is the _Essay on the Human Understanding_, by Locke. It struck down, as with the blow of a hatchet, the wretched mental philosophy of the dark ages,--that philosophy which Puseyism, in its work of diffusing over the present the barbarism and ignorance of the past, would so fain revive and restore, and which has been ever engaged, as its proper employment, in imparting plausibility to error and absurdity, and in furnishing apology for crime. The third was the _Spirit of Laws_, by Montesquieu. It placed legislation on the basis of philosophy; and straightway law began to spring up among the nations out of a new soil. The fourth and last great work--_An Inquiry into the Nature and Causes of the Wealth of Nations_, by Adam Smith--was by far the most influential of them all. 'It is,' says Sir James, 'perhaps the only book which produced an immediate, general, and irrevocable change in some of the most important parts of the legislation of all civilised states. Touching those matters which may be numbered, and measured, and weighed, it bore visible and palpable fruit. In a few years it began to alter laws and treaties, and has made its way throughout the convulsions of revolution and conquest to a due ascendant over the minds of men, with far less than the average obstructions of prejudice and clamour, which check the channels through which truth flows into practice.'