Locke and British Empiricism
Main book by Locke that we’ll focus on: An Essay Concerning Human Understanding. See Book II, Chapter 1, Section 2
For primary and secondary qualities, see Chapter VIII of Book II.
“Empiricism” refers to EXPERIENCE.
Rationalism and Empiricism are the opposites that organize much of the history of psychology. People who believe that knowledge is best obtained through reason are called rationalists. People who believe that knowledge is best obtained through experience are called empiricists. This knowledge source is observation.
So far, the rationalists whom you know about are Plato and Descartes. Aristotle was more of an empiricist, compared to Plato. If knowledge is based on observation, that is called empirical.
The first prominent empiricist we’ll look at now is John Locke. See the Excel chart to find out when Locke lived compared to the others we are looking at.
What Locke is best known for is  the doctrine of the tabula rasa (blank slate) and  dividing experience into primary and secondary qualities. This is a distinction very much like Aristotle’s common sensibles and special sensibles. Galileo and Descartes also recognized this distinction. For Locke, the primary qualities could be about the world, but the secondary qualities were less directly about the world and more directly about the mind.
Idealism and materialism are opposites. Empiricists may be either materialists or idealists. Rationalists are usually idealists.