**Class Schedule:** Thursday, 11:45 - 1:45, Room 7395.

**Textbook:** A pdf of the second edition of the Fitting/Mendelsohn book *First-Order Modal Logic* is available by clicking here. Please download it to your own device rather than working from the web page; it's not an industrial strength site. This is a work in progress, intended for publication with Springer. It is not for distribution. A password will be supplied to decrypt it.

**Instructors:** Melvin Fitting and Richard L. Mendelsohn

**Description/Syllabus:**
Modal logic is usually thought of as the logic of qualified truth: necessarily true, true at all times, and so on. From at least Montague on, quantified modal logic has also been thought of as the natural setting for a logic of intensions. This course will cover the whole range.

We begin with propositional modal logic, presented semantically via Kripke models, and proof theoretically using both tableaus and axiom systems. First-order modal logic will be studied in considerable detail, using possible-world semantics and tableau systems, but not axiom systems. Various philosophical issues will be discussed, amongst which are: the nature of possible worlds, possibilist and actualist quantification, rigid and non-rigid designators, intensional and extensional objects, existence and being, equality, synonymy, designation and non-designation, and definite descriptions in a modal context.

The prerequisites for the course: a familiarity with classical logic, both propositional and first-order.

[Counts towards course satisfaction of Group E]

- Demonstrate familiarity with the most well-known systems of propositional and first-order modal logic;
- Demonstrate familiarity with possible world semantics for propositional and first-order modal systems;
- Provide formal proofs of modal theorems and evaluate the validity of modal arguments using tableaus;
- Demonstrate familiarity with the significance of completeness proofs, and be able to carry out the details in particular examples;
- Represent the various alethic, epistemic, temporal and deontic modalities in terms of possible world semantics;
- Demonstrate familiarity with philosophical problems of identity, existence, designation, and quantification as they relate to the various modalities;
- Understand the formal and philosophical differences between actualist and possibilist quantification;
- Demonstrate familiarity with the De Dicto/De Re distinction and the use of Predicate Abstract Notation to represent it.

The homework is not to be handed in. It will be discussed in class.

**February 9, 2023:**Exercises 5.3.2, 5.3.3, 5.4.3, 5.4.5, 5.4.6**February 16, 2023:**Exercises 7.1.1, 7.1.3, 7.2.1, 7.2.2, 7.2.3, 7.2.4**February 23, 2023:**Exercises 7.4.1, 7.6.4, 7.6.5, 7.6.6**March 2, 2023:**Exercises 8.6.1, 8.7.1**March 9, 2023:**Exercises 9.1.2**March 16, 2023:**Exercises 11.9.1, 11.9.2