Fodor has argued that, because concept acquisition relies on the use of concepts already possessed by the learner, all concepts that cannot be definitionally reduced are innate. Since very few reductive definitions are available, it appears that most concepts are innate. After noting the reasons why we find such radical concept nativism implausible, I explicate Fodor's argument, showing that anyone who is committed to mentalistic explanation should take it seriously. Three attempts at avoiding the conclusion are examined and found to be unsuccessful. I then present an alternative way around Fodor's nativism; I maintain that concepts at a given level of explanation can be semantically primitive, yet at least partially acquired if some of the conditions at a lower level of explanation that are responsible for the concept's presence are themselves acquired.