to be "a method for studying complex systems of empirical relationships". Substantive logic claimed the expression of both the linguistic aspect (formal logic) and logical-ontological, as well as procedural; considered thinking as a historical activity; affirmed the status of logic as an empirical science, the material of which are scientific texts, and the subject matter is the techniques of thinking; considered the instrumental function of logic for scientific thinking. In 1959, Zinoviev considered his concept contradictory, making a choice in favor of mathematical logic. In the monograph "The Philosophical Problems of Multivalued Logic" (1960), Zinoviev reviewed almost all multivalued logical systems, analyzed the place, main results and applicability of multivalued logic in the logic and methodology of science. In subsequent works, he developed his own concept of logic, which he called "complex logic". The problem of logic, according to Zinoviev, was not in formal mathematical calculus, but in the development of "methods of reasoning, proof, methods of scientific knowledge". Zinoviev tried, firstly, to overcome the classical and intuitionistic versions of logic and, secondly, to expand the field of logic research based on the methodology of empirical sciences. The subject of logic is language, it does not discover, but invents specific rules of language — logical rules — and introduces them into language practices as artificial means of systematization. This prescriptivist approach is close to the late Wittgenstein. Zinoviev insisted on the universality of logic, claiming the independence of logical rules from the empirical areas of their application. He denied ontological status to such concepts as a point or zero, considering them tools of knowledge; his approach in Western literature was characterized as logical nominalism. Zinoviev's pupil, the German logician Horst Wessel, noted that his logic was based on syntax, not semantics. Zinoviev investigated a number of questions of non-classical logic, from the general theory of signs to a logical analysis of motion, causality, space and time. In "The Philosophical Problems of Multivalued Logic", multivalued logic was viewed as a generalization, not an abolition of classical two-valued logic, although Zinoviev concluded that the emergence of multivalued logic "dealt a blow" to the a priori classical logic. Later, Zinoviev developed a general theory of succession (the theory of inference), which was significantly different from classical and intuitionistic mathematical logic. According to Wessel, its originality was the introduction of the two-place predicate "from... logically follows..." into the formula for logical following, in fact,