There is a new book on the topic. I think I first came across the connection between Grice and defeasibility in a fascinating paper by Grice entitled "Defeasibility". It was cited by Levinson ("Pragmatics", Cambridge Textbooks in Linguistics). It turned out that Levinson was misquoting from a mimeo by Grice entitled, "Desirability", rather. Ah well.
I had read Baker's contribution to the PGRICE symposium and found it properly obscure ("Alternative mind styles"). This is the late American philosopher G. P. Baker, who succeeded Gric as Tutorial Fellow in Philosophy at St. John's, Oxford. I later learned that Baker was a specialist in festschrift contributions and that he had written one on "Defeasibility and meaning" for a Hart symposium.
I think Hart was Grice's senior, so this post should be entitled Hart and Grice on defeasibility. Or not!
Below the table of contents on the notion.
Of course 'implicature' is defeasible, and the concept very easily (shall we say, proudly?) allows for a formalisation!
------ (ps. Indeed! Hart, b. 1907; Grice b. 1913. They never quite met in the pre-war Oxford, since Grice was merely a 'scholarship boy' from the (West) Midlands, and Hart was pretty rich, and associated with the All Souls 'play group' of J. L. Austin on Thursday nights. Grice never knew of this group. "I had obviously been born on the wrong side of the tracks", he would later regret, :)). Yet, give me the idylic West Midlands countryside any day! Hart, some say, later ceased to be a philosopher, when he just dedicated to _law_; for, as Grice says, "philosophy, like virtue, should be ENTIRE"!
Defeasibility in Philosophy
Knowledge, Agency, Responsibility, and the Law
Edited by Claudia Blöser, Mikael Janvid, Hannes Ole Matthiessen & Marcus Willaschek
Rodopi Amsterdam/New York, NY 2013. VI, 257 pp. (Grazer Philosophische Studien 87)
ISBN: 978-90-420-3761-8 Paper
ISBN: 978-94-012-1011-9 E-Book
Defeasibility, most generally speaking, means that given some set of conditions A, something else B will hold, unless or until defeating conditions C apply. While the term was introduced into philosophy by legal philosopher H.L.A. Hart in 1949, today, the concept of defeasibility is employed in many different areas of philosophy. This volume for the first time brings together contributions on defeasibility from epistemology (Mikael Janvid, Klemens Kappel, Hannes Ole Matthiessen, Marcus Willaschek, Michael Williams), legal philosophy (Frederick Schauer) and ethics and the philosophy of action (Claudia Blöser, R. Jay Wallace, Michael Quante and Katarzyna Paprzycka). The volume ends with an extensive bibliography (by Michael de Araujo Kurth).
Table of Contents
Claudia Blöser, Mikael Janvid, Hannes Ole Matthiessen & Marcus Willaschek: Introduction
Michael Williams: Knowledge, Ascriptivism and Defeasible Concepts
Klemens Kappel: Knowledge, Defeasibility, and the Gettier Problem
Mikael Janvid: The Challenges of Traveling without Itinerary: The Overriding Case
Hannes Ole Matthiessen: Entitlement and Public Accessibility of Epistemic Status
Marcus Willaschek: Strawsonian Epistemology. What Epistemologists Can Learn from “Freedom and Resentment”
Claudia Blöser: The Defeasible Structure of Ascriptions of Responsibility
R. Jay Wallace: Comment on Claudia Blöser “The Defeasible Structure of Ascriptions of Responsibility”
Claudia Blöser: Reply to Wallace
Katarzyna Paprzycka: Can a Spasm Cause an Action? An Argument for Responsibilist Theories of Action
Michael Quante: Autonomous by Default. Assessing “Non-Alienation” in John Christman’s Conception of Personal Autonomy
Frederick Schauer: On the Open Texture of Law
Michel de Araujo Kurth: Selected Thematic Bibliography of Work on Defeasibility in Philosophy and Related Disciplines