A guarantee is a pledge by which a person renders himself responsible to another for something, and binds himself to secure him in the enjoyment of it. The word (_garant_) is derived from the Celtic and Teutonic "warrant." In all the words which we have retained from those ancient languages we have changed the _w_ into _g_. Among the greater number of the nations of the North "warrant" still signifies assurance, guaranty; and in this sense it means, in English, an order of the king, as signifying the pledge of the king. When in the middle ages kings concluded treaties, they were guaranteed on both sides by a considerable number of knights, who bound themselves by oath to see that the treaty was observed, and even, when a superior education qualified them to do so, which sometimes happened, signed their names to it. When the emperor Frederick Barbarossa ceded so many rights to Pope Alexander III. at the celebrated congress of Venice, in 1117, the emperor put his seal to the instrument which the pope and cardinals signed. Twelve princes of the empire guaranteed the treaty by an oath upon the gospel; but none of them signed it. It is not said that the doge of Venice guaranteed that peace which was concluded in his palace. When Philip Augustus made peace in 1200 with King John of England, the principal barons of France and Normandy swore to the due observance of it, as cautionary or guaranteeing parties. The French swore that they would take arms against their king if he violated his word, and the Normans, in like manner, to oppose their sovereign if he did not adhere to his. One of the constables of the Montmorency family, after a negotiation with one of the earls of March, in 1227, swore to the observance of the treaty upon the soul of the king. The practice of guaranteeing the states of a third party was of great antiquity, although under a different name. The Romans in this manner guaranteed the possessions of many of the princes of Asia and Africa, by taking them under their protection until they secured to themselves the possession of the territories thus protected. We must regard as a mutual guaranty the ancient alliance between France and Castile, of king to king, kingdom to kingdom, and man to man.