The article is devoted to one of the topical linguistic problems — the question about the part of the language in forming and firming the knowledge. The main purpose of the work is to present a new linguistic model of the language system of knowledge, the thesaurus net. In order to draw the features of the thesaurus model more clearly, the author considers a number of the most famous linguistic models which have dominated in works since the 20th century. There discussed such models as the language picture of the world, the conceptual system, the mental lexicon, and the information thesaurus. Critical review of linguistic works shows that the thesaurus conception has not been given sufficient consideration. However, this conception corresponds to modern science methodology and must be studied with great attention. In particular, within the thesaurus conception it is possible to restore the objective word network which serves as the main condition for human communication and storage for language knowledge; and network models are supposed to be the most perspective in studying the principles of communication and thinking nowadays. The toughest problem is to find the minimal functional unit of the thesaurus net. In contrast to the other discussed models which only show how the language expresses the knowledge, the thesaurus net is an active semiotic system which enables many different meaning systems.