This argument (to me at least) assumes that the other 4 non-voters would have all voted for ice cream which, by just using basic logic, is false. If 3 out of 5 have already voted to drive off a cliff, one has to assume that at least 2 of the remaining 4 would also vote to drive off a cliff. Now this argument is back to square one… How do we find a solution which doesn’t give ‘driving off a cliff’ as an option in the first place?