Allan Fletcher Gibbard (born 1942) is an American philosopher who is the Richard B. Brandt Distinguished University Professor of Philosophy Emeritus at the University of Michigan, Ann Arbor. Gibbard has made major contributions to contemporary ethical theory, in particular metaethics, where he has developed a contemporary version of non-cognitivism. He has also published articles in the philosophy of language, metaphysics, and social choice theory: in social choice, he first proved the result known today as Gibbard-Satterthwaite theorem, which had been previously conjectured by Michael Dummett and Robin Farquharson.
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👉 Allan Gibbard in the context of Moral sense theory
Moral sense theory (also known as moral sentimentalism) is a theory in moral epistemology and meta-ethics concerning the discovery of moral truths. Moral sense theory typically holds that distinctions between morality and immorality are discovered by emotional responses to experience. Some take it to be primarily a view about the nature of moral facts or moral beliefs (a primarily metaphysical view)—this form of the view more often goes by the name "sentimentalism". Others take the view to be primarily about the nature of justifying moral beliefs (a primarily epistemological view)—this form of the view more often goes by the name "moral sense theory". However, some theorists take the view to be one which claims that both moral facts and how one comes to be justified in believing them are necessarily bound up with human emotions.
Popular historical advocates of some version of the moral sense theory or sentimentalism include the 3rd Earl of Shaftesbury (1671–1713), Francis Hutcheson (1694–1746), David Hume (1711–1776), and Adam Smith (1723–1790). Some contemporary advocates include Michael Slote, Justin D'Arms, Daniel Jacobson, Jesse Prinz, Jonathan Haidt, and perhaps John McDowell. Simon Blackburn and Allan Gibbard endorse a non-cognitivist form of sentimentalism.
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Allan Gibbard in the context of Gibbard's theorem
In the fields of mechanism design and social choice theory, Gibbard's theorem is a result proven by philosopher Allan Gibbard in 1973. It states that for any deterministic process of collective decision, at least one of the following three properties must hold:
- The process is dictatorial, i.e. there is a single voter whose vote chooses the outcome.
- The process limits the possible outcomes to two options only.
- The process is not straightforward; the optimal ballot for a voter "requires strategic voting", i.e. it depends on their beliefs about other voters' ballots.
A corollary of this theorem is the Gibbard–Satterthwaite theorem about voting rules. The key difference between the two theorems is that Gibbard–Satterthwaite applies only to ranked voting. Because of its broader scope, Gibbard's theorem makes no claim about whether voters need to reverse their ranking of candidates, only that their optimal ballots depend on the other voters' ballots.