
Principles of Human Knowledge and Three Dialogues
Nothing exists but minds and what minds perceive, Berkeley argues, and matter is a word philosophers cannot cash. God does the perceiving that keeps your furniture there once you leave the room.

Nothing exists but minds and what minds perceive, Berkeley argues, and matter is a word philosophers cannot cash. God does the perceiving that keeps your furniture there once you leave the room.

Reality is made of monads, mind-like simple substances with no windows, whose perceptions God synchronized in advance. His conclusion that ours is the optimal world drew Voltaire's ridicule in Candide.