Under the influence of the constitutional ideas of Frederick the Great, and the crop of new ideas borne by the French Revolution, the conception of the State has completely changed since the turn of the century. The patrimonial state of the Middle Ages was the hereditary possession of the Sovereign. Hence sprung the modern State, which represents the reverse of this relation, in which the Sovereign is the first servant of the State, and the interest of the State, and not of the ruler, is the key to the policy of the Government. With this altered conception of the State the principle of nationality has gradually developed, of which the tendency is as follows: Historical boundaries are to be disregarded, and the nations combined into a political whole; the State will thus acquire a uniform national character and common national interests. This new order of things entirely altered the basis of international relations, and set new and unknown duties before the statesman. Commerce and trade also developed on wholly new lines. After 1815 the barriers to every activity--guilds and trade restrictions--were gradually removed. Landed property ceased to be a monopoly. Commerce and industries flourished conspicuously. "England introduced the universal employment of coal and iron and of machinery into industries, thus founding immense industrial establishments; by steamers and railways she brought machinery into commerce, at the same time effecting an industrial revolution by physical science and chemistry, and won the control of the markets of the world by cotton. There came, besides, the enormous extension of the command of credit in the widest sense, the exploitation of India, the extension of colonization over Polynesia, etc." England at the same time girdled the earth with her cables and fleets. She thus attained to a sort of world-sovereignty. She has tried to found a new universal Empire; not, indeed, by spiritual or secular weapons, like Pope and Emperor in bygone days, but by the power of money, by making all material interests dependent on herself. Facing her, between the Atlantic and Pacific Oceans, linking the West and the East, the United States of North America have risen to be an industrial and commercial power of the first rank. Supported by exceptionally abundant natural resources, and the unscrupulously pushing character of her inhabitants, this mighty Empire aims at a suitable recognition of her power in the council of the nations, and is on the point of securing this by the building of a powerful navy.