This is Edition 2017. Read the NEW Edition 2021 at https://dspace.lu.lv/dspace/handle/7/53914. Hyper-textbook for students in mathematical logic. First order languages. Axioms of constructive and classical logic. Proving formulas in propositional and predicate logic. Glivenko's theorem and constructive embedding. Axiom independence. Interpretations, models and completeness theorems. Normal forms, skolemization and resolution method. Herbrand's theorem.
Sections 1, 2, 3 represent an extended translation of the corresponding chapters of the book: V. Detlovs, Elements of Mathematical Logic, Riga, University of Latvia, 1964, 252 pp. (in Latvian).