The development of linguistic thought in the second part of the eighteenth century is examined from two perspectives, anthropological and epistemological. The author shows that the sensualist tenet that linguistic signs have a formative influence on thought gradually lost ground. For Rousseau, following (and criticizing) Condillac, language is a key to the evolution of society and owes its genesis to social factors (needs and passions) and natural causes. Their intensity leads to different language types and means of cognition. In this context. various questions proposed for the Berlin Prize dealt with language (cf. essays by Michaelis, Süßmilch, Herder). The ideologues continued Condillac’s epistemological legacy and sought to provide education in proper thinking, by analyzing ideas with the aid of linguistic signs. However, some ideologues revised/limited the cognitive function of language (‘desemiotization’ of linguistic theory). Maine de Biran stressed the value of inner life against external sense experience (activity vs. sensitivity dualism). Other approaches to language study are considered: the Scottish school and Reid’s ‘common sense’ theory; Schlegel’s views on philology as art, language genesis, and the organic character of inflected languages. Kant’s transcendentalism questions the prevalent cognitive model and omits language altogether (vs. non-verbal categories) for the validation of truth.