Homework on §1.4—assigned Fri 9/5 and due Mon 9/8

For each of the following claims of entailment, describe a counterexample—that is, a possible world that shows the claim is false. (To describe the possible world, just say what truth values the sentences φ, ψ, and χ would have in it.)

(i) φ, ψ ⇒ χ
(ii) ψ, χ ⇒ φ

Could one possible world serve as counterexample to both claims? (Say why or why not.)