The blank slate theory is a theory, proposed by British philosopher John Locke, that human minds start off empty, as blank slates, and are filled in by personal experiences. According to Locke, thoughts begin by absorbing sensation and become more complex through reflection on what is sensed.
John Locke puts forth his theory in Book II of his work, "An Essay Concerning Human Understanding," first published in 1670. He calls the mind a "tabula rasa," or blank sheet or writing tablet. The essay states that though humans are born without content, they have the basic faculties to absorb and process content once they acquire it. According to Locke, the three types of actions performed on simple ideas consist of combining simple ideas into complex ideas, comparing simple ideas without uniting them and forming abstractions from particulars. In addition, other faculties, such as memory, store ideas. In the essay, Locke goes on to explain how sensation and reflection produce such concepts as time, space, number, solidity, power, identity and moral relations.
Locke was not the first philosopher to compare the mind to a blank writing surface. In the fourth century B.C., in his work "De Anima," Aristotle makes a similar proposition. Locke's essay, however, was widely read and a great influence on future generations of thinkers.