Locke's political theory was founded upon that of social contract. Unlike Thomas Hobbes, Locke believed that human nature is characterised by reason and tolerance. Like Hobbes, Locke believed that human nature allowed people to be selfish. This is apparent with the introduction of currency. In a natural state, all people were equal and independent, and everyone had a natural right to defend his "life, health, liberty, or possessions." Most scholars trace the phrase "Life, Liberty and the pursuit of Happiness," in the American Declaration of Independence, to Locke's theory of rights, though other origins have been suggested.