[EM] Herve Moulin's proof not really a proof

[Kevin Venzke]

Hi Nicholas,

At no point is he adding simultaneously different groups of voters.
He is reaching conclusions about one group and then modifying it
to get the new group, but the modification is always relevant to
Participation.

Let me try to understand which stage exactly it is that you do not
agree with. Again let me start with the idea that you believe that
the winner of the first election (the one with four voting groups)
can only be A, in order to satisfy Condorcet and Participation.

Step 0: Assume A must win (everybody agrees nobody else is possible)
Case 1: proved that D cannot win (you agree with this)
Case 2: proved that B cannot win (you agree with this)
Case 3: proved that C cannot win (you agree with this)
Case 4: proved that either A or C must win in this election:
3 voters vote A > D > C > B.
3 voters vote A > D > B > C.
5 voters vote D > B > C > A.
4 voters vote B > C > A > D.
4 voters vote C > A > B > D.
Do you disagree with that? The new voters are C>A voters so the
new winner cannot be anybody worse than A, because we know that
A was previously winning.

I will wait to continue until you say whether you agree that the 
winner of that five-faction election must be A or C.

Kevin