[EM] Condorcet Criterion for plurality.

[Markus Schulze]

Dear Mike,

you wrote (13 Dec 2000):
> My point was not that IIAC is no good because Plurality
> meets it. My point was that IIAC means that Approval, and
> even Plurality, are better than IRV, for all those people
> who bring up Arrow's criteria.

The intention of IIAC is to guarantee that the result of
the elections cannot be manipulated by running additional
candidates who change the result of the elections without
being elected. But you define IIAC is such a manner that
even plurality --which is highly vulnerable to this strategy--
meets this criterion. Therefore your definition of IIAC has
nothing to do with the original intention of this criterion.
Therefore --and this is what Blake is saying-- you have to
present an additional justification for your definition of
IIAC. And in so far as you are unwilling or unable to
justify your definition of IIAC, the usefulness of your
"universally accepted" concept is questionable.

You wrote (13 Dec 2000):
> Layton asked for uniformity, and I have to agree with
> him that Markus's system (if it uses different rules for
> different methods) is quite useless for compring voting
> systems, because uniformity of criterion application rules
> is necessary for comparing methods by criteria.

If you had read Craig Layton's mails more carefully, you
would have observed that he wrote (13 Dec 2000): "It doesn't
make sense to define systems with reference to themselves,
which is what MIKE is attempting to do, because this makes
it impossible for any meaningful kind of comparison between
systems."

Markus Schulze