John Locke (1632–1704) was an English philosopher who is primarily known for three main things: (1) founding the school of empiricism; (2) promotion of his political theories; and (3) his view of qualities.
In regard to empiricism, Locke argued that the foundation for knowledge comes from experience, not intuitive reasoning or innate ideas. Thus, experience imprints knowledge. According to Locke, the mind of a person at birth is a tabula rasa —a “blank slate.” He promoted empiricism in his work, Essay Concerning Human Understanding.
In his work, Two Treatises of Government, Locke espoused a political theory that denied the theory of “divine right of kings” and its view that the king’s authority comes directly from God and not the people. For Locke, sovereignty belongs to the people, not the government. He also believed that a government should have a system of checks and balances. Locke argued that all people have natural rights in regard to life, liberty, and property. The purpose of government was to protect these rights. If the state does not protect natural law, the people can remove or alter it. Thus, rebellion can be justified under certain conditions. Although he died seventy years before the American Revolution, many of his political ideas were adopted into the U.S. Constitution.
Locke was also known for his views on qualities. He asserted that objects have two qualities—primary and secondary. Primary Qualities are the qualities of a thing that exist independently of a perceiver. For example an object’s shape and size are fixed whether a perceiver is viewing the object or not. On the other hand Secondary Qualities are the qualities of a thing that depend for their existence on a perceiver. Examples include areas like sound and taste which appear to be relative to a perceiver.