Spooner was an American individualist anarchist with radical opinions on everything. His true calling was writing pamphlets and books on issues of the day. His private postal service was forced out of business by the government. He again lost everything and lived out his years as an urban recluse. His most famous work was The Unconstitutionality of Slavery. No Treason is his most famous political tract (1867). "Although Spooner’s argument on the unconstitutionality of slavery had no legal basis, his concept of natural law contained the germs of anarchistic theory of government".