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.