Of fundamental importance to the development of the idea of natural rights was the emergence of the idea of natural human equality. As the historian A.J. Carlyle notes: "There is no change in political theory so startling in its completeness as the change from the theory of Aristotle to the later philosophical view represented by Cicero and Seneca.... We think that this cannot be better exemplified than with regard to the theory of the equality of human nature."[9] Charles H. McIlwain likewise observes that "the idea of the equality of men is the profoundest contribution of the Stoics to political thought" and that "its greatest influence is in the changed conception of law that in part resulted from it."[10] Cicero argues in De Legibus that "we are born for Justice, and that right is based, not upon opinions, but upon Nature."[11]