Modal Logic

A watercolor of Ruth Barcan Marcas painted in red and yellow hues on grid-lined paper.

Ruth Barcan Marcus was an American philosopher who developed the Barcan formula, which will be covered in session 18. (Image courtesy of Elisabeth Steinacher on flickr. Used with permission.)


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Spring 2015



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Course Description

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Course Description

Modal logic is the logic of necessity and possibility, and by extension of analogously paired notions like validity and consistency, obligation and permission, the known and the not-ruled-out. This a first course in the area. A solid background in first-order logic is essential. Topics to be covered include (some or all of) the main systems of propositional modal logic, Kripkean "possible world" semantics, strict implication, contingent identity, intensional objects, counterpart theory, the logic of actuality, and deontic and / or epistemic logic. The emphasis will be more on technical methods and results than philosophical applications.

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Stephen Yablo. 24.244 Modal Logic. Spring 2015. Massachusetts Institute of Technology: MIT OpenCourseWare, License: Creative Commons BY-NC-SA.

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