Ernest Belfort Bax was among the most original and gifted of the first generation of Marxists in Victorian England, and an intimate of luminaries such as William Morris, who considered him the philosopher of the movement. He had first-hand experience of the 19th century tradition of German philosophy which so profoundly influenced Karl Marx, and was a close friend of Engels. Bax was a prolific writer and speaker, the organizer of the Second International, leader of English Social Democracy and a colleague of all the leading European social democratic intellectuals of his time. This biography of Bax sets him in his privileged Victorian middle-class context, analyzes his political and intellectual development, and assesses his achievements and their significance for his own time and later.