After teaching mathematics and physics in Ghana with the Peace Corps (1963-1965), Gibbard studied philosophy at Harvard University, participating in the seminar on social and political philosophy with John Rawls, Kenneth J. Arrow, Amartya K. Sen, and Robert Nozick. In 1971 Gibbard earned his Ph.D., writing a dissertation under the direction of John Rawls. Soon after his doctoral degree, Gibbard provided a first proof of a conjecture that strategic voting was an intrinsic feature of non-dictatorial voting systems with at least three choices, a conjecture of Michael Dummett and Robin Farquharson.
Gibbard
Michael Dummett