The phenomenon of similarity or attribute agreement gives rise to the debate between realists and nominalists. Realists claim that where objects are similar or agree in attribute, there is some one thing that they share or have in common; nominalists deny this. Realists call these shared entities universals; they say that universals are entities that can be simultaneously exemplifi ed by several different objects; and they claim that universals encompass the properties things possess, the relations into which they enter, and the kinds to which they belong.