Arrow imposed D in conjunction with the requirement U that the domain is completely unrestricted. Perhaps this condition expresses something closer to its intended meaning then. With an unrestricted domain, a dictator, unlike Zelig, is someone whose preferences conflict with everybody else’s in a range of cases, and it is in each instance his preferences that agree with social preferences, not theirs. However this may be, the example of Zelig shows that whether it is appropriate to impose D on social welfare functions depends on the details of the choice problem at hand.  The name of this condition is misleading. Sometimes there is nothing undemocratic about having a “dictator”, in Arrow’s technical sense.