Lecture 5 (Modality) Ling 442

Exercises (part1) Translate the following English sentences into Predicate Logic. Every student is serious. Mary met some candidate. Sue has a red car. All definite NPs (the …) should be treated as names (at least for now). Ten dollars should also be treated as a name.

Exercises (part 2) Identify each use of modal in terms of (i) type (epistemic or deontic) and (ii) force (possibility or necessity). i. Mary must be home by now since she left an hour ago. ii. Bill must have smoked at the party because he is a heavy smoker. iii. You may not smoke here because this building is a non-smoking facility. iv. Everybody must abide by the rules. v. Sue may or may not come. Who knows? She is so whimsical. vi. I may have lost my wallet. What should I do? vii. In order to take Semantics II, you must have taken Semantics I (already).

Possible worlds What is a possible world? A complete specification of how things are, or might be, down to the finest semantically relevant detail There is only one “real world”. By changing some details of the real world, you “create” a different possible world. Intuitively, a world is like the collection of all facts. But in our theory, a world is a primitive.

Counterfactual conditionals If kangaroos had no tails, they would topple over. Assume counterfactually that the antecedent is true. Make minimum adjustment to the actual world for this to be possible. Check to see if the consequent is true on these assumptions.

deontic vs. epistemic modality deontic modality: having to do with obligations of various sorts necessity (must) vs. possibility (may) epistemic modality: having to do with (the speaker’s) knowledge

Semantics of modal verbs Quantifiers over possible worlds (with some restrictions.