Universals

Let us observe the sun, an orange, a lemon, a banana, and a yellow car. We could ask, whether all of those things have some thing in common, something we would call ``yellowness''. Is there an individual being such as ``yellowness''? There are two beliefs among philosophers, and the problem of universals is deciding, which is right. Platonic realists believe, that there is some nonphysical being called ``yellowness'', that stands in some relation to all yellow objects. This being is a ``universal''. The opposing view is the one of nominalists, which believe, that there is no such thing and that all yellow objects have nothing in common except being called ``yellow''. Therefore they get the name ``nominalists''.

It is agreed that universals have to satisfy at least the following conditions:

• Universals can be multiply instantiated.
• Universals are abstract.
• Universals are the referents of general terms.