This monograph has as its objective to give a critical survey of the development of the theories concerning the essence, the function, and the most characteristic (determining) features of language, and to explore and evaluate the motive forces responsible for this development. The author explains mainly the progressive elements of the theoretical foundations and methodological procedures of different times and schools (trends), and places them in the process which presents the course of development of linguistic theory as an organic whole. He deals in detail with the foreign (mainly American) and Hungarian monographic publications based on so-called modern methodologies and, in the light of the facts of language, points out the theoretical (gnoseological, philosophical) errors which, of course, are errors from the point of view of general linguistics, too. He relies on a Marxist-based interpretation of the modern concept of natural and social law for the formulation of his own conception of linguistic law which includes also his own view of linguistics structures.