The great thinker from whom the basic ideas of what we shall call constructivist rationalism received their most complete expression was René Descartes. But while he refrained from drawing the conclusions from them for social and moral arguments, these were mainly elaborated by his slightly older (but much more long-lived) contemporary, Thomas Hobbes. Although Descartes’ immediate concern was to establish criteria for the truth of propositions, these were inevitably also applied by his followers to judge the appropriateness and justification of actions.
Thomas Hobbes