Answer:
Social contract: this idea was developed by English philospher John Lock. It consists in the vision that governments are a social contract between rulers and the ruled, and as a result, governments should have the consent of the governed, otherwise, they deserve to be toppled.
Division of powers: this idea was developed by French philospher Montesquieu. He developed a mode of government that the majority of the world uses to this day. A government divided in three branches of power: the executive (president), the legislative (congress), and the judiciary (courts).