Review of topics covered before the midterm exam

Sections 1.1-1.4 [Mendelson]
propositional connectives, truth tables, tautologies, logical implication or
consequence, substitution, propositions as descriptions of truth functions,
Axiom systems, well-formed formulas, proofs, theorems, decidable, Modus Ponens,
Deduction theorem, soundness (every theorem is a tautology), completeness
(every tautology is a theorem)

Section 2.1-2.8 [Mendelson]
quantifiers, free, bound variables, free for x in B, first-order language,
interpretation, model, soundness, completeness for first-order logic,
satisfiability, first-order theories, logical axioms, proper axioms, rules of
inference.  Generalization, Natural Deduction rules (see slides set ln6.pdf),
proofs of soundness, completeness, consistent, deduction theorem,
Equivalence theorem, replacement theorem, rule C (EI), closed form, complete
theories, Lindenbaum's Lemma (complete extensions of consistent theories),
scapegoat theories, Godel's completeness theorem, Skolem-Lowenheim theorem
(denumerable models), theories with equality, testing whether a theory is a
theory with equality, normal models, quantified quantifiers ("there exist
exactly n entities such that ...", logical validity,
logical inference, |=, |-