The theorem states that if a voting system satisfies:
Complete and transitive social preferences;
Universal domain, i.e., any individual preference ordering is allowed;
Pareto efficiency (or unanimity); and
Independence of irrelevant alternatives (IIA);
then there must exist a
Dictator. Well, don't forget that the theorem gots its own name, that is, ARROW's impossibility theorem.
So, just remember: Cupid's Arrow!!
HT to Uncle Marcus.