Nominalism

Nominalism is the metaphysical doctrine about reality that asserts that abstract objects and/or universals do not actually exist on the account of being non-spatiotemporal (not existing in space or time) objects while being causally inert (not in cause-effect relations with other objects), hence they are only names or conceptual heuristics. Its implication asserts that everything is particular or concrete. There are two kinds of nominalism: the rejection of abstract objects (contra Platonism) and the rejection of universals (with universals being those things that may be instantiated in particular objects, though existing independently per se). A nominalist may deny both or just one. Though the rejection of abstract objects and universals are independent from one another, both kinds share similar arguments. In terms of abstract objects, one argument against such is an appeal to Ockham’s razor, wherein one should not posit entities unnecessarily. If it is possible to demonstrate how concrete objects can perform the theoretical role of abstract objects, then one should avoid postulating abstract objects. George Berkeley in fact declared that using abstract terminology and universals is not only unnecessary but is the chief source of human error and mistake (due to their vague idea causing miscommunication, etc.). There is also the epistemological argument - since abstract objects are causally inert, it is challenging to understand how one can obtain reliable knowledge about them (which is similar to the doubts of that of empiricism). Further, abstract ideas are difficult to form in the mind within reference to particular objects, so how exactly does the process of abstraction work to remove all particular features to arrive to the general? As well, the ontology of abstract objects is not comprehensive. Similarly, there is also an appeal to Ockham’s razor as an argument against universals - if it is possible to demonstrate how particulars can play the theoretical role of in re universals (universals that exist within their instances and assumedly exist inside space and time), then there should be no reason for universals to exist. There are also more difficult challenges for universals, such as a version of Bradley's regress problem. Suppose that 'a' instantiates universal B. This instantiation, i, would be classified as a relation. A, b, and i are all connected by another instantiation, ii, because there needs to be something that qualifies that relation in the first place. Since ii is also a relational factor, then there is another instantiation iii connecting A, b, i, and ii, and so on ad infinitum. And infinite regresses in philosophy are considered to be incoherent, and thus universals are as well. Nominalism is a very popular position - though of course it has its critics.