John Locke was an English scholar and one of the great philosophers and political thinkers of the late seventeenth and early eighteenth century. His most famous philosophical essay “Concerning Human Understanding” aimed to determine the limits of human understanding. He attempted to explain how we can understand morality with the same precision we can know mathematics, because we are the creators of moral and political ideas.
Locke's great political works, and the ones with which he is most associated, are the Two Treatises on Government. While they were published after the Glorious Revolution of 1688, which brought William of Orange to the English throne, they were written in the post Civil War reign of  Charles II in the early 1680s. In these Treatises, Locke explains his theory of natural law and natural rights, which he uses to distinguish between legitimate and illegitimate governments. He also argues for the legitimate necessity of political revolt against tyrannical governments. These ideas would gain hold in Enlightenment thinkers and would be cited as important influences in the founding principles of the French and American Revolutions.
Locke was born in Somerset, England in 1632. He attended Westminster School and then Christ Church College, Oxford. He eventually left the University with a degree in medicine. At the same time he became a member of the Royal Society, a scientific institution where he became friends with fellow member Isaac Newton.
He also made friends with the future Earl of Shaftesbury, whose political round tables had a profound influence on Locke. Locke left medicine and became assistant to Shaftesbury, becoming his principle secretary when the Earl became Lord Chancellor in 1672.
During this time, the Restoration period, Locke wrote a "Letter Concerning Toleration" in which he argues for acceptance of religious dissenters and a separation between church and state. Given Locke's high profile, his ideas on freedom of religion and the rights of citizens were considered a challenge to the King's rule and in 1682 Locke went into exile in Holland. There he completed “An Essay Concerning Human Understanding.”
Locke had also been implicated with a group of English revolutionaries who had advocated the overthrow of Charles II and the English government tried to extradite him. Charles II died before that occurred and Charles’ successor, the Catholic James II, was eventually overthrown by a protestant parliamentary revolt. William of Orange was invited to bring a Dutch force to England and take the thrown. Known as the Glorious Revolution of 1688, power in English government switched from King to Parliament. Locke was free to return to England and did soon the same ship that carried Princess Mary to join her husband King William.
Locke had written Two Treatises of Civil Government in the early 1680s while in exile and in 1690 was finally able to publish them. Their success also allowed him to finally publish An Essay Concerning Human Understanding, in which he established the principles of modern Empiricism, and attacked the rationalist concept of innate ideas.
Locke took a number of posts in the new government and continued to write on a wide variety of subjects including economics, philosophy and theology.
He retired from public life in 1695 and continued to revise his Essay Concerning Human Understanding and participate in debates. He died in 1704.

Second Treatise on Government

In Two Treatises of Government, Locke defended the proposition that government rests on popular consent and rebellion is permissible when government subverts the ends for which it is established, namely the protection of life, liberty, and property.
Rather less popular today than the second Treatise, Locke's First Treatise was a systematic attack on Sir Robert Filmer and his 1680 work “Patriarcha,” a passionate defense of divine monarchy. But a closer reading also shows that Locke was also attacking the far more powerful political teachings of Thomas Hobbes and his work “Leviathan.”
Locke's Second Treatise, remains the more influential work. In it, Locke sets forth his theory of natural law and natural rights; in it, he shows that there does exist a rational purpose to government and one need not rely on "myth, mysticism, and mystery."
Despite his advocacy for rebellion in extraordinary circumstance, Locke argued that one must defend government as an institution against anarchy. Locke's object was to insist not only that the public welfare was the test of good government and the basis for properly imposing obligations on the citizens of a country; but, also, that the public welfare made government necessary.