He also did much to extract the philosophy of his day from scholastic and ancient Greek thinking.
Locke is best known for his Essay Concerning Human Understanding in which he states his views on the nature of human knowledge and understanding. This work had a major impact on the empirical philosophy that succeeded the continental rationalism of Descartes.
As a personal friend of two renowned scientists of the time, Robert Boyle and Isaac Newton, Locke was intent on setting the foundations of human knowledge within a scientific framework.
After reading Descartes' Meditations, he rejected the rationalist philosophy and indicated that there could be not innate knowledge. He argued that everything we know derives from experience or, in other words, the actions of the physical world on our senses. He put forth that the mind at birth is like a blank slate or tabula rasa, and experience alone is the source of our ideas.
According to Locke, ideas of sensation come from our sensory experience when our sensory apparatus accesses the world. Ideas of reflection come from the introspection of our sensory experience.
Experience, in the form of sensations and reflections, provides raw materials to the mind, which then works with, analyzes and organizes them in complex ways. Simple ideas are such things as cold, hot, sweet and sour and contain no other ideas, nor can be created by us. Complex ideas, on the other hand, are produced by the mind from simple ideas and are the product of internal mental operations.
In his work Two Treatises of Civil Government Locke set out his political philosophy and established himself as a political theorist of the highest order. In it he argued against the divine right of kings and maintained that all men are free and equal in the state of nature and possess certain natural rights.
In contrast to Thomas Hobbes' position that only an absolute ruler can save a person in the state of nature from the brutality of others, Locke argued that people form a government as a state of convenience. The social contract is one drawn between the people and their appointed or chosen representatives.
Locke's political doctrines were incorporated into the American Constitution and into the constitution established in France in 1871.
Since John Locke's philosophical and political views were widely understood and favorably welcomed by many of his contemporaries, he has been described by Bertrand Russell as "the most fortunate of philosophers.".