[EM] Chris's letter revisited

[Michael Ossipoff]

In replying to some parts of this message, I was a bit hasty, so I’ll take 
it over (Wouldn’t it be great if _anything_ could be taken over?):

Pasting from Mike's page: > /Some definitions useful in subsequent criteria 
definitions:/ > > A voter votes X over Y if he votes in a way such that if 
we count only > his ballot, with all the candidates but X & Y deleted from 
it, X wins. > > [end of definition] > > Voting a preference for X over Y 
means voting X over Y. If a voter > prefers X to Y, and votes X over Y, then 
he's voting a sincere > preference. If he prefers X to Y and votes Y over X, 
he's falsifying a > preference. > > A voter votes sincerely if he doesn't 
falsify a preference, and > doesn't fail to vote a sincere preference that 
the balloting rules in > use would have allowed him to vote in addition to 
the preferences that > he actually did vote. > > [end of definition] > > > 
Strategy-Free Criterion (SFC): > > /Preliminary definition: /A "Condorcet 
winner" (CW) is a candidate > who, when compared separately to each one of 
the other candidates, is > preferred to that other candidate by more voters 
than vice-versa. Note > that this is about sincere preference, which may 
sometimes be > different than actual voting. > > > SFC: > > If no one 
falsifies a preference, and there's a CW, and a majority of > all the voters 
prefer the CW to candidate Y, and vote sincerely, then > Y shouldn't win. > 
 > [end of definition] > Michael Ossipoff wrote: > Kevin and Chris posted 
their criteria that they incorrectly claimed > equivalent to SFC. > > These 
same alternative "SFCs" have been posted to EM before and > thoroughly 
discussed before. > In fact, we've been all over this subject before. So why 
don't you point us to where in the EM archive we can find this earlier 
discussion?

Chris asked:

Are they [votes-only, rank-methods-only versions of my criteria] in your 
opinion equivalent for ranked-ballot methods?

I reply:

Yes, probably so. It seems a sure thing that there’s no way that RV, 
Approval or any other nonrank method could meet SFC, GSFC, or SDSC.

Though I object to the suggestion to replace my criteria with those 
versions, I don’t deny that someone could consider them more convenient, as 
_tests_ for compliance with the criteria. As I said, when telling why I like 
or don’t like a method, I want to do so in terms of criteria whose wording 
tells why one should want compliance. So I prefer my own preference-based 
wordings of my defensive strategy criteria. However, I myself have used a 
votes-only, rank-methods-only test for compliance with my criteria: Steve 
Epplely’s Beatpath Criterion. Any rank method that meets BC meets all four 
majority defensive strategy criteria (SFC, GSFC,. WDSC, & SDSC). You could 
say that no nonrank method meets BC, or you could say that it’s only applied 
to rank methods. But it’s a convenient way to test for compliance with all 
the majority defensive strategy criteria. BC’s wording doesn’t make it 
obvious why it should be met, and so I prefer my criteria, as criteria. I 
use BC as a test.

So I can’t say that I object to the use of votes-only, rank-methods-only 
tests for compliancd with my criteria, if someone finds them more convenient 
to use.

I’d said:

>Though Chris's and Kevin's criteria clearly are not equivalent to SFC, > 
>maybe someone could write a votes-only cirterion that is. First of > all, 
>what's this obsession about "votes-only"?

Chris replied:

Some people worry that criteria that give the appearance that we have to 
read voters' minds to see if they are met are not the easiest to check for.

I reply:

As I was saying, I have no objection to votes-only, rank-methods-only 
compliance tests. In fact I use one myself: I use BC because it tests for 
compliance with all four majority defensive strategy criteria.

On the other hand, I usually prefer to demonstrate compliance directly from 
my criteria definitions. It isn’t as difficult as one might expect. I 
understand the objection about preferences being intangible, and how someone 
might prefer to only work with votes. But preferences aren’t difficult too 
deal with. I probably could have been clearer about that before, so let me 
say it better:

First, compare the preference stipulations in the criterion’s premise with 
the preference stipulations in the claimed failure example. Those in the 
latter should be consistent with those in the former, in order for the 
criterion to apply to that example.

Given the preferences stated in the example, and the voting stated in the 
example, use the definitions of sincere voting and falsified voting (those 
definitions use “prefer”) to determine whether the example is consistent 
with the criterion’s premise stipulations about sincere voting &/or 
non-falsified voting.

If the example is consistent with the criterion's premise in that and other 
respects, then the criterion applies to the example. If so then check if the 
example's result complies with the criteerion's requirement.

All of that can be done without using or having a definition of “prefer”. 
(Though I’ve posted to EM a precise, abstract definition of “prefer”).

And no mind-reading is needed, because the failure-example-writer tells you 
explicitly what voters’ preferences are. He can, in his 
criterion-failure-example, make those preferences whatever he chooses.

More work than a votes-only, rank-methods-only compliance test? Maybe, but I 
consider it more effective to demonstrate compliance or noncompliance 
directly in terms of my preference-based criteria. But I’ve used BC as a 
test to determine compliance. In fact, I’ve used BC to _demonstrate_ 
compliance to another person, when that person asked for demonstrations for 
all the defensive strategy criteria. But usually I prefer demonstrations 
that directly work from the actual criteria definitions, the 
preference-based definitions that, in my opinion, best tell why compliance 
is desirable.

The rest of my reply was ok as-is.

Mike Ossipoff