[EM] Arrow's Theorem.

[Markus Schulze]

Dear Eric,

FPP is a preferential method according to the definition
of preferential methods. First: FPP can be applied to
every possible set of orders of merit; the FPP winner is
the candidate with the largest number of first preferences.
Second: The FPP winner doesn't depend on information
that is not included in the set of orders of merit.

Approval Voting is not a preferential method. Approval
Voting cannot be applied to every possible set of orders
of merit; Approval Voting can only be applied to sets of
dichotomous ballots.

Average Rating and Median Rating are no preferential
methods since the winners depend on information that
is not included in the set of orders of merit.

Markus Schulze