This paper tries to elucidate Bentham's political ideas in terms of philosophical radicalism. First, his utilitarianism was a call for a way of thinking radical enough not only in his time, but also nowadays. There still are a vast number of cases where conflicts can be reconciled peacefully by utilitarian approaches, although his idea of a "moral arithmetic" is certainly fallacious. Second, Bentham considered society, law and even nature as fictitious entities. This is a point which has not been adequately understood since, but touches right at the conceptual foundation upon which our understanding of human lives can be built. Elucidation of these two points will show how radical Bentham's philosophy is.