The Problem of Universals
by Dr. Jan Garrett
Last revised date: November 12, 2004
Extreme Realism, Moderate Realism, Conceptualism, and Nominalism are answers to the question: what sort of reality do the general things--what Aristotle called species and genera--so important to scientific and metaphysical knowledge have?
The Medieval Platonist answer is that these things are the Forms or Ideas. They exist apart from particulars and they are most real. Humanity exists apart from particular humans and is more real than the particulars are. The particulars are sort of copies of the Form. This view is sometimes called Extreme Realism. (The Platonic form or idea is a universale ante rem.)
The Aristotelian answer, sometimes called Moderate Realism, is that the general things, or universals, exist in two ways, first as forms or general structures within particulars and common to particulars of a given species; second as general ideas in the mind of persons who know those forms. Thus humanity exists in particular human beings and in the idea of the philosopher who knows what it is to be human (universale in re and universale in mente).
By contrast with such extreme and moderate realisms, Nominalism is the view that there are only individual things and that such entities as species and genera (human and tiger, animal and plant) do not exist except as mere words or puffs of air (nuda nomina, flatus vocis) referring to similarities among individuals. Thus, for a nominalist, there is no human nature, just Tom, Dick, Harry, and Sally, who happen to resemble one another in various ways.
Conceptualism holds that species and genera are concepts or abstract ideas created by the human mind after experience with particular or individual things (a concept is a universale post rem); our knowing makes use of the general concepts our minds have created, but these concepts do not refer to general things existing outside mind.
John Locke's view of abstract ideas seems very close to conceptualism. In attacking Locke's position on abstract ideas, George Berkeley and David Hume seem to adopt a nominalist position.
Notes
1. "Universale ante rem" literally means the universal prior to the (particular) thing.
2. "Universale in re" literally means the universal in the (particular) thing; "universale in mente" means the universal in the mind (i.e., after it has been abstracted from similar particulars).
3. "Universale post rem" literally means the universal created (by the mind) after (experience of) a set of similar particular thing(s).