natural law
In an unpublished manuscript on "The State of War" Rousseau elaborates on this point: "If natural law were inscribed only on human reason, it would hardly be capable of directing most of our actions. But it is also indelibly engraved in the human heart. It is from the heart that natural law speaks to man more powerfully than all the precepts of philosophers." Grace G. Roosevelt, Reading Rousseau in the Nuclear Age (Philadelphia: Temple University Press, 1990), p. 189.