Social contract (consent of the governed), and the common good of the people.
Freedom, natural rights, and self-determination
The relationships between governments and the people they governed, and limited government.
Enlightenment brought with it great advances which, together with the Industrial Revolution, made room for the profound political change determined by the French Revolution. The forerunner of this movement was the French mathematician Rene Descartes (1596-1650), considered the father of rationalism. In his book Discourse of Method, he recommends, in order to get to the truth, to doubt everything, even the seemingly true things. From rational doubt one can reach the understanding of the world, and even of God.