J. A. Comenius’ interest in the didactic of languages was not marginal, but was related to his all-reformative efforts. The results of this part of his work are mostly valid even today. Comenius is the first Czech linguist and his conception of language is still up-to-date. He links up linguistic events with the psychological and social context, in a similar way as present-day semantics and psycho-linguistics do. In the human universe there is a harmonious correlation of things, thinking and language, while the unit of speech is the triunity of thing-concept-word. The study of the nature of language not only served Comenius as a basis for working out the didactic of languages, including practical textbooks, but also led him to propose a universal language of communication. In the interest of the comprehensive reform the proposed artificial language is to be rational, analogical and harmonious. Of particular interest is Comenius’ endeavour to make use of the phonological symbolism of sounds so that words by their sound alone may suggest the essence of a thing. Comenius recognizes the historical conventionality of languages, but sees a practical deficiency in it. In the didactic of languages Comenius emphasizes the connection of speech with activities in the same way as thinking is connected with hand. He proceeds from the observation of child speech, draws attention to the interference of languages and anticipates present-day theories of the internalization of external behaviour of languages. He resolves the dispute of the direct method and the grammatical one synthetically from the viewpoint of the aim, which is both the practical and the formal aspect. Therefore he places the rule between an example and an exercise. He calls for conscious acquisition of grammar for didactic as well for formally educational reasons. In textbooks Comenius was always concerned with the parallelism of language, education and factual instruction. The connection of “languages and sciences” In the Gate is in fact the first outline of pansophia, and its Czech version is the first description of the world for classroom teaching. At the same time Comenius is opposed to excessive extension of factual instruction in language textbooks and is against sensuousness, which leads to irrationality. The sentence examples in his textbooks have not the same function as the sentence patterns in the current laboratory method.