Binswanger discusses the historical problem of “universals” and the reasons why the traditional alternative solutions to it – realism and nominalism – fail to solve the problem. He then shows how Ayn Rand’s theory of concepts succeeds due to its novel conceptions of abstraction and similarity, and of the role of measurement integration. Binswanger also explains the role of conceptual common denominators and ends the lesson with a look at the crucial “some, but any” principle.