Abstract: If representation is resemblance, how we do we think of groups or classes of things? According to a tradition Berkeley opposed—a tradition represented by Locke—we do so by forming abstract or incomplete ideas. I show that Berkeley's opposition does not depend on his own personal failure to form abstract images, but on what he took to be the impersonal or objective impossibility of abstract objects. Berkeley himself accounts for general thinking not in terms of abstract or incomplete ideas, but in terms of our selective attention to ideas both concrete and determinate. Contentful thought about the natural world is impossible without ideas as objects, Berkeley believes, but ideas do not, in his view, completely fix the content of our thought.

Keywords: abstract idea, abstract object, abstraction, content, Locke, representation, resemblance, selective attention,