The aim of this project is (1) to address Immanuel Kant’s view that a ‘transcendental grammar’ can be extracted from the pure concepts or ‘categories’ of the understanding, and (2) to seize this intriguing view as an opportunity to reconstruct, in Kant’s name, a characteristically Kantian theory of (i) the origin of language, and (ii) the relation between thought and language. In 18th-century Europe, one of the most animated philosophical debates turned around the question of how to explain the transition from animalistic cries and gestures to the cognitive use and mastery of words. It seems that Kant, with his idea of a ‘transcendental grammar’, was on his way to developing his own account of this problem - i.e., of the origin of language. In this regard, this research hypothesizes that in Kant’s system, transcendental grammar is a science resulting from the application of transcendental logic to our capacity to speak and hear, qua material phenomenon organized in space and time. In order to probe the viability and possible implications of this hypothesis, I reconstruct two dialogues on ‘transcendental grammar’: firstly between Kant and his student J.G. Herder, and secondly between Kant and W. Von Humboldt, in the wake of the disagreement between Kant and Herder. On this basis, I probe the involvement of the laws of transcendental logic in the constitution of words - as what transcendental grammar is suspected to be about.