Cappelen received a BA in Philosophy, Politics, and Economics from the University of Oxford, Balliol College, in 1989.
[8] Cappelen's most influential work is the 2004 book, Insensitive Semantics (written with Ernest Lepore).
The book defends a minimal role for context in semantics and advocates speech act pluralism.
[9] The first monograph on the topic, it surveys both historical and contemporary work on conceptual engineering, and presents a theory of its nature and limitations.
[11] Along with Josh Dever, Cappelen has argued that the notion of perspective is unimportant for the philosophy of language, thought, and action.
[12] Cappelen has also authored, or co-authored, important books on the debate between contextualists and relativists (Relativism and Monadic Truth, with John Hawthorne), and on quotation (Language Turned on Itself with Ernest Lepore).
[17] Along with John Hawthorne and Tamar Gendler he coedited The Oxford Handbook Of Philosophical Methodology (2016).