This chapter seeks to understand the nature and the significance of Berkeley's crucial distinction between ideas and notions. Ideas are treated as the passive objects of mental perception, while notions are immediately known mental acts.
Ideas provide us with sensory knowledge of bodies (construed idealistically), while notions mark the transparency of our own doings and our active spiritual natures. It is argued that the doctrine of notions is a significant part of Berkeley's system, accounting for our knowledge not only of the inner, but also of intellectual elements such as "substance," "causal power," "relation," and "unity." The doctrine of notions thus represents a rationalist strand in Berkeley's philosophy, and it is suggested, by way of conclusion, that it should lead us to question the routine categorization of Berkeley as an empiricist.