Book Review: Introduction to Mathematical Logic,
Leon Henkin · Bulletin of the American Mathematical Society · 1957
with relative admissibility ( §7), two major though probably corrigible errors occur.First, as H. B. Curry discovered, the rule a, b-*a/\b is not relative admissible, e.g., in the system whose only rules are + and +a->0.Second, a/\b^>a is not admissible, e.g., in the system whose only rules are + and +a-\->++a+ and (£>?).Despite all these shortcomings, which probably require a thorough revision to overcome, the book constitutes an essentially sound and indeed outstanding contribution.