 Just as thoughts are composed of concepts, many concepts are themselves complex entities that are composed of other concepts or more basic representational components. In this section, we look at different proposals about the structure of what are often called lexical concepts. Roughly speaking, these are concepts that tend to be associated with individual words in natural language—concepts like BIRD and WALK as opposed to manifestly complex concepts like NOCTURNAL ANIMALS THAT LIVE IN TREES or TO WALK AIMLESSLY ON A NEWLY PAVED ROAD. With BIRD and WALK and similar concepts, it isn’t obvious what type of internal structure (if any) they have, and this has led to a great deal of controversy (Margolis &amp; Laurence 1999, Murphy 2002). Accounts of the structure of lexical concepts have focused on concepts for categories of objects, actions, and events rather than concepts for individuals. Our discussion will share this focus (see, e.g., Blok et al. 2005 and Levine 2010 for discussion of concepts of individuals).