Malebranche argues that ideas are representative beings existing in God. He defends this thesis by an inference to the best explanation of human perception. It is well-known that Malebranche's theory of vision in God was forcefully rejected by philosophers such as Arnauld, Locke, and Berkeley. However, the notion that ideas exist in God was not the only controversial aspect of Malebranche's approach. Another controversy centered around Malebranche's view that ideas are to be understood as posits in an explanatory theory. Opponents (...) of this approach, including Arnauld and Locke, held that our talk about ideas was not explanatory but instead merely descriptive: we use the word 'idea' to describe phenomena that we observe by reflecting on our own minds. This controversy has not received much attention from scholars, but in the present paper I will show that it was an explicit and important subject of concern for Malebranche, Arnuald, Locke, and Berkeley and that attention to this controversy can illuminate several aspects of these philosophers' work. (shrink)