[EM] minimal defense & SDSC

[Markus Schulze]

Hallo,

I wrote (2 Feb 2004):

> In so far as election methods are defined only on the cast
> preferences and not on the sincere preferences, whether a
> given election method satisfies a given criterion must be
> reflected in the way this method uses the cast preferences.
> Therefore, there is no need to include the sincere
> preferences in the definition of a criterion.
>
> Mike Ossipoff wrote (2 Feb 2004):
>
> > It isn't entirely clear what you mean. For example, some of
> > us would like to require a method to not give voters defensive
> > strategic need to bury their favorite, at least under conditions
> > under which there are methods that won't do that.  Are you saying
> > that that requirement can be made by a motivational statement
> > instead of by the criteriion.
>
> For example, Steve Eppley uses the following formulation
> in his website:
>
> > minimal defense: If more than half of the voters prefer
> >   alternative y over alternative x, then that majority must have
> >   some way of voting that ensures x will not be elected and
> >   does not require any of them to rank y equal to or over any
> >   alternatives preferred over y. (Another wording is nearly
> >   equivalent: Any ordering of the alternatives must be an
> >   admissible vote, and if more than half of the voters rank y
> >   over x and x no higher than tied for bottom, then x must not
> >   be elected. This criterion, in particular the first wording,
> >   is promoted by Mike Ossipoff under the name Strong Defensive
> >   Strategy Criterion. Satisfaction means a majority can defeat
> >   "greater evil" alternatives without having to pretend to prefer
> >   some compromise alternative as much as or more than favored
> >   alternatives. Since voters in public elections cannot be
> >   relied upon to misrepresent their preferences in this way,
> >   non-satisfaction means that elites will sharply limit the
> >   set of nominees that voters are asked to vote on, by offering a
> >   system in which there are only two viable parties, each of which
> >   nominates only one alternative.)

Steve Eppley wrote (11 Feb 2004):

> Markus has taken an excerpt out of context, and in this
> case it is misleading. (Perhaps I should search my election-
> methods-list folder to see how often my writing has been
> misrepresented.)  Here's more of what I actually posted at
> the webpage Markus cited, which shows how Markus distorted
> my definition:
>
>    minimal defense:  If more than half of the voters prefer
>    alternative y over alternative x, then that majority
>    must have some way of voting that ensures x will not
>    be elected and does not require any of them to rank y
>    equal to or over any alternatives preferred over y.
>    (Another wording is nearly equivalent: Any ordering
>    of the alternatives must be an admissible vote, and
>    if more than half of the voters rank y over x and
>    x no higher than tied for bottom, then x must not
>    be elected.  This criterion, in particular the first
>    wording, is promoted by Mike Ossipoff under the name
>    Strong Defensive Strategy Criterion. -snip- )

Sorry, I wasn't aware that my quotation could be misleading.

Markus Schulze