John Locke (1632–1704), who was also mostly known as a political philosopher, divided ideas into two classes: sensation, our initial sense impressions; and reflection, the mind’s actions on the initial sense impressions. Thus he distinguished between perception and cognition. Further, he considered our complex ideas (abstract concepts such as justice, love, whiteness) to derive from combinations of simple ideas. The notion that cognition develops from the simple to the complex anticipates Piaget and other twentieth- century cognitive psychologists.