Like David Kaplan, this thinker showed that, given universal instantiation, modal logic with propositional quantifiers leads to a Russell-like paradox in the paper “On a Family of Paradoxes.” This thinker observed that, in standard deontic logic, “you ought to help someone who has been robbed” entails “someone ought to have been robbed,” a result known as the Samaritan Paradox. In correspondence with this thinker, a teenage Saul Kripke proposed the branching theory of time; that prompted this thinker to distinguish between “Piercian” and “Ockhamist” theories in the book (*) Past, Present, and Future. (10[1])This thinker’s paper “The Runabout Inference-Ticket” imagined a logical operator with the introduction rule for disjunction and the elimination rule for conjunction, which he dubbed “tonk.” For 10 points, name this philosopher who invented modern tense logic. ■END■