Radical (Lat. radix, a root), in English politics, a term applied to politicians who desire to make thorough, or radical, changes in the constitution and in the social order generally. Although it had been used in a somewhat similar way during the reign of Charles II., the term Radical, in its political sense, originated about the end of the 18th century, probably owing its existence to Charles James Fox, who, in 1797, declared that "radical reform" was necessary. The ideas of the first Radicals were borrowed largely from the authors of the French Revolution. The word was more generally employed during the disturbed period between the close of the Napoleonic wars and the passing of the great Reform Bill of 1832, and was applied to agitators like Henry Hunt and William Cobbett. After the Reform Bill had become law, the advocates of violent change were drawn into the Chartist movement, and the Radicals became less revolutionary both in speech and object. Thus in 1842 an observer writes:"The term Radical, once employed as a name of low reproach, has found its way into high places, and is gone forth as the title of a class who glory in their designation." About this time many members of Parliament were known as Radicals, among these men being George Grote and Joseph Hume. The Radicals never formed a distinct party in the House of Commons, and subsequently they formed simply the advanced section of the Liberal party. For a few years in the 19th century the wearing of a white hat was looked upon as the distinguishing mark of a Radical, a hat of this colour having been worn by Hunt when addressing meetings.
See W. Harris, History of the Radical Party in Parliament (1885); S. Bamford, Passages in the Life of a Radical (new ed., 1893); C. B. Roylance Kent, The English Radicals:. an Historical Sketch (1899).