Philosopher and Empiricist
Locke, a member of a middle-class Puritan family, left studies of the church to pursue the vociation of a physician. While at Oxford, he became friends with Isaac Newton and Robert Boyle. After leaving in 1683 over disagreements about the Catholic king, Charles II, he finished his Essay.
This four-book work discusses questions of awareness and reality; Locke believed that we can only think about non-mental entities by being aware of mental entities that represent them. In building this relationship, he wrote that we must control our belief-forming capabilities -- it is our duty to do so. In the spirit of Newton and Boyle, his method consists of first collecting data for and against the proposition (hypothesis) in questions. Second, that data is analyzed for relevance, and then the proposition is judged on that evidence.
Locke's Second Treatise of Government a defining work in the soon-to emerge American government, was based on Locke's concept of natural law. Locke believed that just as with mathematics, the laws of nature could also be deduced through experimentation. The hinge of the work was the concept of private property. In Locke's "state of nature" (a through experiment depicting ancient man), an individual successfully convinced others that a particular plot of land was "his". He combined his labor with this object or plot, and thus it became property. This posession can only be freely contracted away to others, and most importantly, government. This is the "liberal theory of state" on which is based the Declaration of Independence, written about seventy years later.