[EM] Does the 'Independence of Irrelevant Alternatives Criterion' Imply a

[James Green-Armytage]

Forest Simmons <fsimmons at pcc.edu> writes:
>To make this really simple, suppose that there is only one chooser, and
>that there are three choices, and that the chooser prefers A to B to C to
>A, with varying levels of intensity.  Suppose that the chooser finally
>decides to choose A.  But before announcing her decision she finds out
>that option B has been withdrawn.  Is she going to stick with A?
>
>In other words, not even a dictator method can satisfy the IIAC at the
>fundamental level of actual preferences.

	I have to say that I don't think it makes sense for an individual to
prefer A to B, B to C, and C to A. It's just logically contradictory.
Individual preferences should be assumed to be transitive. 
	What Condorcet discovered is that a set of individuals with transitive
preferences between a set of options can sum up to a society that has
intransitive preferences with regard to those options. 
	Arrow's theorem is based on this idea. He believed that the possibility
of intransitive social preferences was fundamentally disturbing, and in
that I quite agree with him. Not only does it lead to ambiguous election
results, but it also seems to be the source of the inevitable
vulnerability of voting methods to strategic manipulation, which is a
grave problem for majority rule voting.

James