In addition to concepts and conceptual senses, Frege holds that there are extensions of concepts. Frege calls an extension of a concept a ‘course of values’. A course of values is determined by the value that the concept has for each of its arguments. Thus, the course of values for the concept __ is a dog records that its value for the argument Zermela is the True and for Socrates is the False, and so on. If two concepts have the same values for every argument, then their courses of values are the same. Thus, courses of values are extensional.