The paper describes an approach to the formation of logic ontology based on descriptions of objects in terms of the predicate calculus language. The main tool for creating such a description is an extraction of an elementary conjunction of predicate formula literals that is isomorphic to subformulas of some given formulas. The
definition of an isomorphism of elementary conjunctions of atomic predicate formulas is given. The method of ontology construction is formulated. An illustrative example of such a construction and expansion of ontology is presented.