 Lange agrees with Trendelenburg that logic, like epistemology of science, ought to concern itself with an analysis of necessity, which informs Lange’s response to Herbart. However, Lange disagrees with Trendelenburg on the status of logic. Trendelenburg was what might be called a neo-Aristotelian logician. He wrote several works on Aristotelian logic, especially the logic of the categories. As such, Trendelenburg works on what Lange refers to as the “traditional logic of content”. Lange considers that this has been superseded by the new, English “logic of extension,” associated with John Venn and others.