One of the intellectual traditions which stands behind modern classical liberalism is that of natural law and natural rights. This tradition emerged in the 17th and 18th centuries and argues that the world is governed by natural laws which are discoverable by human reason. Human beings, because of their particular natures have a number of natural rights, or what Tom Paine described as “imprescriptible rights”. According to the founding fathers of the American constitution these rights are the right to life, liberty, property, and the pursuit of happiness. A key aspect of this intellectual tradition is the notion that natural rights are not created by government but exist anterior to it and that governments are in fact created to “secure these rights.” During the 19th century the natural law/rights traditions was overtaken by English utlitarianism which argued that the government should pursue policies which would do “the greatest good for the greatest number.”
Liberty Fund is publishing an extensive collection of works about natural law in its Natural Law and Enlightenment Series including works by Hugo Grotius, Samuel von Pufendorf, and Francis Hutcheson.
See also the following schools of thought which supported the natural law and natural rights tradition:
And the 19th Century Utilitarians which did not.
For further reading on this topic see the works listed below: