On the Arrow and Wilson impossibility theorems

A social welfare function is Arrovian if it is transitive-valued and satisfies IIA. We examine the logical relation between the statements (A) If f is Arrovian with domain ℘ then it is dictatorial if it satisfies the Pareto criterion and (W) If f is Arrovian with domain ℘ then it is dictatorial or inversely dictatorial if it is non-null and satisfies non-imposition. We exhibit a class of domains on which W implies A and another on which A implies W. We also present examples of domains on which one of the statements is true and the other is false.