When Descartes died in 1650, John Locke was eighteen. He had read Descartes. He approved the new science and vaguely accepted the notion of innate ideas. Like Descartes he saw no apparent contradiction between scientific reason and royal authority or established religion. By the time he wrote his major works a decade later in the 1660s-Two Treatises of Government and An Essay concerning Human Understanding-a change had occurred in his thinking. There were no more innate ideas. At birth the mind is a blank slate. The basis of knowledge is human experience.
So appears John Locke, first in the celebrated line of British empiricists who cleared away the last remnants of medieval essence and put science on a solid experimental basis. For Locke reason was innate but not as necessary truths accessible to introspection. Reason is a human faculty, limited in scope and exercised at will. As a result, belief is always unsteady and fallible. Those who cannot or will not accept its limits, those who persist in fanatically defending or imposing dogmatic theological or metaphysical principles, can and should be resisted along with the clerical or monarchical institutions that support them. In this way, restraints on free inquiry will be lifted and proper productive use made of practical knowledge.
The reason for Locke's change of heart was less philosophical argument than politics. In 1667 Locke, an Anglican don, was hired as secretary to the powerful and wealthy Anthony Ashley Cooper, future Earl of Shaftesbury. Shaftesbury-leader of the opposition to the Stuart monarchy, avid encloser and developer of a vast hereditary domain, founder of the Carolina colony, promoter of free trade, mercantile profit, and colonial expansion-had more than an academic interest in epistemology. As the earl's resident philosopher, Locke's job was to fashion arguments that would discredit the earl's monarchist enemies and justify a government friendly to the interests of property