How Logic Works: Errata

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(p 104) In the statement of Existential Elimination, the formula should be ∃x ϕ(x) with an “x” after the existential quantifier.

(p 145) The argument here shows the uniqueness of intersection (if it exists), but there needs to be a separate argument for the existence of the intersection. Such an argument can be given using the naive comprehension axiom, or more rigorously, the Axiom of Separation.

(p 146, line 1) The statement should be A ⊆ B if and only if A ∩ B = A.

(p 170, line -3) The statement of “totality” should read ∀x∀y(x ≠ y → (Rxy ∨ Ryx)).

(p 215, line 18) “completeness” ⇝ “complete”

(p 232) The statement of EE should include the restriction that the arbitrary name “a” does not occur in the conclusion ψ of the subproof.