 One of the better-known terms of Leibniz’s philosophy, and of his philosophy of mind, is “apperception.” A famous definition is presented in section 4 of the Principles of Nature and of Grace (1714), where Leibniz says that apperception is “consciousness, or the reflective knowledge of this internal state.” He adds that this is “something not given to all souls, nor at all times to a given soul” (G VI, 600/A&amp;G 208).