 Once again the key step is establishing the relevant disjunction as a pragmatically inferred instance of the Law of Excluded Middle, e.g., “Either mammals lay eggs or mammals don’t lay eggs”. In fact, this practice was first identified by Aristotle (Soph. Elen. 175b40–176a17), who offered an early version of the all-or-none (or both-or-neither) in arguing that a negative answer to a “dialectical” or conjoined question like “Are Coriscus and Callias at home?” would imply that neither is at home, given the default supposition that they are either both in or both out. Once again LEM applies where it “shouldn’t”; \(A \vee © A\) behaves as though it were an instance of \(A \vee \neg A\), triggering the disjunctive syllogism: