Hofstadter lists dozens of complex concepts we use fluently—'solar system,' 'slam dunk,' 'beltway,' 'plagiarism,' 'Wikipedia,' 'Bose-Einstein condensation,' 'quantum cryptography,' 'baby boomer,' 'the Fed,' 'pork belly futures,' 'affirmative action,' 'presidential lecture'—showing the remarkable range and depth of human conceptual systems.