The point being that striving to write up a perfect definition that can be universally among players is a little pointless anyways. Just as long as were all on the same page and when the games over, we both know who won.
The point is that there are games where big money is involved and "being on the same page" just isn't going to be enough. A well defined ruleset is necessary for a game where the outcome really counts. That being said, I see "A player must deduct one point for every necessary eye he has on the board" as a well defined rule which could be unambiguously applied (a definition of a "necessary eye" would be added, but that's a detail).