T he term "idea" in the seventeenth century is notoriously difficult. Not only does each major thinker have their own understanding of "idea"-many of those thinkers themselves move ambiguously between different meanings. This confusion is generally attributed to Descartes. While ideas had only existed in the mind of God, Descartes consciously made new use of the term by applying it to things in human minds. At the same time, Descartes left many questions about what an idea is. Given Descartes' own ambiguity, the various doctrines of ideas developed by Arnauld, Malebranche, Locke, Spinoza and Leibniz, all have some legitimate claim as interpretations of Descartes. 2 Compared with these Cartesian ambiguities, Leibniz' doctrine of ideas appears relatively clear. Leibniz wrote several short but explicit accounts of ideas, and the "Discourse on Metaphysics" and the New Essays have significant discussion of ideas as well. 3 Because of these explicit accounts, Leibniz' theory of ideas is usually given unproblematically as one of "dispositions" or "faculties," as if this were a sufficient account of ideas. Clearly such an account is not sufficient, unless accompanied by some account of what dispositions are for Leibniz, and the existence of dispositions in a monad presents difficulties. In a similar way, the connection between innate ideas, reflection, and necessary truths is often taken as unproblematic. Nicholas Jolley, however, particularly emphasizes the difficulties involved in Leibniz' account of this connection. 4 In this paper, I will first examine what an idea is for Leibniz, and then use this account to explain Leibniz' doctrine of self-reflection. In both cases, I will focus on the relationship between his theory of ideas and the rest of his philosophical system. What Leibniz says about ideas is fairly clear-the difficulty is detennining what he means and how his claims fit with his conception of monads. In order to address these latter difficulties, I will begin by examining three broader factors in Leibniz' theory of ideas. II 1) Thinking of a thing does not necessarily mean having an idea (Jf that thing. In the "Discourse on Metaphysics," Leibniz makes a distinction between notions or concepts, and ideas: "Thus, the expressions in our soul, whether we conceive them or not, can be called ideas, but those we conceive or form can be notions,