Hugo Grotius (in Dutch, Huigh de Groot [1583–1645]) modified natural law from a prescription for the common good to a doctrine restraining what individuals were permitted to do in pursing their own separate goods. That is, he changed Thomas Aquinas’ (c. 1225–1274) notion of natural law from a communal idea to an individualistic one. This line of thought was highly influential for the political philosophy developed by both Thomas Hobbes (1588–1679) and John Locke (1632–1704).

According to Grotius in The Law of War and Peace (1626), natural law could be used to settle religious disputes, as well as international ones. Grotius thought that natural law could be known by observing human nature. He concluded that humans are both sociable and combative and that every person has rights that limit what others can do. Government is the result of sacrificing some rights so that our lives will improve. Grotius thought that we would be obligated to obey natural law if God did not exist, although he also thought that God does enforce natural law.

Both Hobbes and Locke constructed theories of just and useful government, beginning from foundations of natural law. However, Hobbes emphasized the combative aspects of human nature, whereas Locke emphasized the sociable side.