Karl Brugmann (1849-1919) was one of the central figures in the circle of Neogrammarians who rejected a prescriptive approach to the study of language in favour of diachronic study. This short overview of the development of comparative Indo-European linguistics and philology in the second part of the nineteenth century was first published in 1885, the year before Brugmann's celebrated multi-volume comparative grammar of Indo-European began to appear. To Brugmann, language is not an autonomous organism that develops according to inherent laws. It exists only in the individual speaker, and every change in a language takes place because of the speaker, though speakers share similar psychological and physical processes. Traditional philologists, including Brugmann's former university teacher Georg Curtius (1820-1885), were extremely hostile to the Neogrammarians' approach. Here, Brugmann responds to Curtius' criticism and defends his research methodology and theories.