His abiding interest in medicine led to his striking an acquaintance with the politician, Anthony Ashley Cooper, known to history as the Earl of Shaftesbury. This was the turning point in Locke's life, as from then on his destiny was irrevocably linked with Shaftesbury's. Locke gave up his scientific inclinations and took a keen interest in affairs of the state. The year 1675, found him in France as a consequence of the liberal Shaftesbury having incurred the wrath of the royals. When Locke returned in 1679, he found a nation rife with political upheaval and a monarchy hostile towards Protestants and removed himself to Holland. Following the revolution of 1688, he returned to England, where he stayed till his death.
Throughout his life, Locke wrote on a wide variety of subjects. His Treatises of Government and Essay Concerning Human Understanding are famed in the annals of political thought and philosophy as invaluable contributions. That aside, he distinguished himself with well written pieces in the fields of economics, science, theology and education. According to Haworth, "It would be no exaggeration to describe him as the political philosopher who laid the moral foundations of the modern world view" (100).
Locke's Essay Concerning Human Understanding was his first and only foray into the realms of epistemology, the branch of philosophy that studies the nature of knowledge. Divided into four books, his essay is a detailed theory of knowledge and aims to " discover what kind of things God has fitted us to know, and so how we should direct and use our intellect and understanding" (Woolhouse 78). At the onset he emphasizes the importance of experience in the pursuit of knowledge and dismisses the notion that ideas are innate. According to Locke the mind is a blank slate on which ideas are inscribed by the hand of experience. He states that experience of the senses is the tool used in gleaning knowledge and rationale must be used before a thorough understanding of raw information is possible. Thus "Locke's empiricism about ideas is combined with rationalism about knowledge" (Woolhouse 79). He further differentiates between simple and complex ideas. The former are the components out of which the latter are constructed.
Finally Locke defines knowledge as "The perception of the connection and agreement, or disagreement of any of our ideas" (qtd. in Woolhouse 80). From this definition it is clear that he believes acquisition of knowledge depends primarily on perception or on the ability to make pertinent connections between related ideas. This point of view brings out the limitations in acquiring knowledge. "Locke's general conclusion concerning the extent of our knowledge is then, that God has also put within the grasp of our rationality 'the way that leads to a better life' and given us the means to acquire knowledge of 'whatever is necessary for the information of virtue'" (Woolhouse 83). Locke's doctrines influenced epistemology and served as the foundation on which later philosophers based their work.
His Political Theories
Locke's Two Treatises of Government emerged from the Exclusion Crisis. During this period, the Earl of Shaftesbury was waging a struggle to prevent the ascension of the Catholic James, Duke of York, the brother of the reigning monarch, Charles II, to the throne of England.