Are All Universals Instantiated?

In contemporary metaphysics the struggle between realism and nominalism is apparent and important, but it tends to overshadow the struggle within realism itself. As a realist, D.M. Armstrong is very aware of this internal struggle and forms a theory of universals at the heart of this issue. His theory is based on the naturalistic notion that the physical universe is all that there is. This naturalism leads him to formulate the Principle of Instantiation, stating that all universals must be instantiated in a particular. That is, there can be no universals that are uninstantiated and thus reside in what has become known as a “Platonic heaven”. Many other realists challenge the Principle of Instantiation and claim that realism yields a Platonic realm of the Forms that houses all universals. These other realists also argue that contrary to Armstrong’s view realism is not compatible with naturalism. In this paper, I argue that Armstrong’s theory of universals has the resources to resist this criticism. I will show that by adopting his theory of universals, the combination of realism and naturalism is attainable. Along with this combination and the Principle of Instantiation, Armstrong maintains a legitimate theory, which holds strength within this metaphysical debate.