Understand the Philosophical Theories of Nominalism and Realism

Is the world made up of universals and particulars?

woman's hand holding an apple
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Nominalism and realism are the two most distinguished positions in western metaphysics dealing with the fundamental structure of reality. According to realists, all entities can be grouped into two categories: particulars and universals. Nominalists instead argue that there are only particulars. 

How Do Realists Understand Reality?

Realists postulate the existence of two kinds of entities, particulars, and universals.

Particulars resemble each other because they share universals; for example, each particular dog has four legs, can bark, and has a tail. Universals can also resemble each other by sharing other universals; for example, wisdom and generosity resemble each other in that they are both virtues. Plato and Aristotle were among the most famous realists.

The intuitive plausibility of realism is evident. Realism allows us to take seriously the subject-predicate structure of discourse through which we represent the world. When we say that Socrates is wise it is because there are both Socrates (the particular) and wisdom (the universal) and the particular exemplifies the universal.

Realism also can explain the use we often make of abstract reference. Sometimes qualities are subjects of our discourse, as when I say that wisdom is a virtue or that red is a color. The realist can interpret these discourses as asserting that there is a universal (wisdom; red) that exemplifies another universal (virtue; color).

How Do Nominalists Understand Reality?

Nominalists offer a radical definition of reality: there are no universals, only particulars. The basic idea is that the world is made exclusively from particulars and the universals are of our own making. They stem from our representational system (the way we think about the world) or from our language (the way we speak of the world).

Because of this, nominalism is clearly tied in a close manner also to epistemology (the study of what distinguishes justified belief from opinion).

If there are only particulars, then there is no "virtue," "apples," or "genders." There are, instead, human conventions that tend to group objects or ideas into categories. Virtue exists only because we say it does: not because there is a universal abstraction of virtue. Apples only exist as a particular type of fruit because we as humans have categorized a group of particular fruits in a particular way. Maleness and femaleness, as well, exist only in human thought and language.

The most distinguished nominalists include Medieval philosophers William of Ockham (1288-1348) and John Buridan (1300-1358) as well as contemporary philosopher Willard van Orman Quine.

Problems for Nominalism and Realism

The debate between supporters of those two opposed camps spurred some of the most puzzling problems in metaphysics, such as the puzzle of the ship of Theseus, the puzzle of the 1001 cats, and the so-called problem of exemplification (that is, the problem of how particulars and universals can be related to each other).)  It;s puzzles like these which render the debate regarding the fundamental categories of metaphysics so challenging and fascinating.