In metaphysics, there have been countless arguments to prove the existence, or absence, of certain kinds of things, such as universals. There have been several attempts find a solution to the problem of universals, an unresolved issue which revolves around the question of whether or not universals actually exist, and if so, which particular form they take. Though there are many possible solutions to this question, in modern metaphysics one of the most popular stances on the issue is Realism, which can be further boiled down into two popular schools of thought, Aristotelian realism and Platonic realism. Although both forms of realism agree that universals are actual entities, they are distinguished by their contradictory views on the independence of universals. Aristotelian realism asserts that universals exist exclusively as properties instantiated by particulars, while Platonic realism suggests that universals can exist as entities separate of their particulars. However, with regards to the problem of universals, this distinction is negligible because both forms of realism use the same essential logic to attempt to prove the existence of universals. Realism hinges upon the idea that in order for certain phrases and ideas to be true, universals must be considered distinct entities. For example, consider the statement “the sky is blue.” There is a known entity, the sky, that, in all senses of the word, can be accurately described as being blue. This much is indisputably true. But why, of all the possible colors that could be have been used to describe the sky, was “blue” chosen? By itself, the word blue is inherently meaningless, nothing more than a random jumble of letters. Yet, the word is allowed to have meaning because somewhere along the line it was assigned to a property that appears in the physical world. The same property that is exemplified by the sky, a sapphire, and countless other “blue” particulars. A property that must exist, for how else would it be possible to accurately say that the sky is blue, or, for that matter, that anything is anything at all? According to realists, this reasoning in itself is sufficient to commit us to the existence of universals.
Although realism is a popular answer to the problem of universals, there exists another widely-held stance known as resemblance nominalism. This particular school of thought asserts that there are no such thing as universals, simply individuals and the resemblances they share amongst each other. In a sense, nominalism is the antithesis of realism, for a number of reasons. For instance, nominalists have never been satisfied by realists' ability to define the exact boundaries of universals. Realists have suggested that within any one universal there exist infinitely varying degrees of that universal, such as the color blue encompassing the color cerulean, which explains the large amount of variability among particulars that seem to instantiate the same universals. And though this sort of reasoning is sufficient for realists, the concept of universals within universals is still largely irrelevant to nominalists. This is due to the fact that nominalists firmly believe that human beings are incapable of defining exactly what a universal's ideal form is without referencing it against itself, which in itself is a cyclical paradox. And without this ideal form, there is no way to know where one instantiation of a universal stands in relation to the true universal. When does the the color blue stop being blue and become purple? And who has the right to define such borders? In addition, many nominalists argue that universals simply cannot exist due to the fact that they are meant to represent singular entities yet defy a very basic law of physics by being capable of existing in multiple places simultaneously. Platonic realists have suggested that this can be explained by the fact that universals may exist outside of the physical universe, freeing them from the constraints of the laws of physics. However, nominalists have asserted that this type of argument, and realism in general, violates the Principle of Simplicity, a key component of theory building that advocates the use of theories that postulate the least amount of entities. And if the Principle is assumed to be true, then it must follow that nominalism is the more logical solution to the problem of universals, for it attempts to explain the universe in terms of particulars exclusively. By eliminating universals altogether, nominalists have essentially made the claim that what people assume to be universals are nothing more labels given to groups of individuals that resemble one another enough to be categorized under the same universal. It is with this claim that nominalism attempts to disprove realism and solve the problem of universals, and in fact would be quite successful at doing so if not for the fact that, according to realism, resemblances fall within the scope of what is considered a universal. A fact that allows the realism versus nominalism debate to reach full circle and leave the problem of universals ultimately unanswered.
The problem of universals is just one example of the many metaphysical issues that revolve around the existence of certain intangible things. Another issue that has been hotly contested in metaphysics is the importance of unactualized possible things. Certain philosophers, such as the Wyman referenced by Quine in his essay “On What There Is,” have made the claim that it would be inaccurate to say that entities do not exist simply because they lack actualization, or the property of having physical form at a given moment. For example, consider the sentence “the son of Barack and Michelle does not exist.” If this sentence is assumed to be a truth, it would suggest that there is no such thing as the son of the current president and his wife. However, if the son does not exist, how is that he is capable of being spoken of? This can be explained by the fact that because it is possible to conceptualize the son of Barack and Michelle, he as an individual has being as an unactualized but possible existence. In other words the sentence merely claims is that the son lacks actualization, not that he does not exist at all. This is important in understanding Wyman's definition of what it means to “be,” which claims that if actualization is assumed to be a property, it is not necessary for something to be actualized to exist, the same way an apple does not have to be red in order to exist. With this reasoning, Wyman is capable of arguing that it is important to acknowledge unactualized possible things, for to do otherwise would be equivalent to disregarding the existence of countless entities for no other reason than the fact that they lack the property of actualization.
The commitment to Wyman's belief may be tempting, but it can be avoided if one were to consider Russell's Theory of Descriptions. This theory asserts that it is possible to utilize seeming names and descriptive phrases without supposing the existence of the named entities, which can be accomplished by analyzing the names and phrases in virtue of the sentences in which they occur. Before analysis, the descriptive phrase “the son of Barack and Michelle” can be supposed by philosophers like Wyman to require some sort of objective reference in order to have meaning, at which point the being of the son has been established. However, Russell's theory can be used to explain the sentence “the son of Barack and Michelle does not exist” as meaning “Someone is the son of someone named Barack and someone named Michelle, and this person does not exist.” By translating the sentence this way, the burden of objective reference is transferred from the descriptive phrase to the bound variables, in this case the word “someone.” Bound variables are unique in that they can simultaneously be assigned to entities and yet somehow act not as names. This is due to the fact that they are capable of referring to the entities in the most general terms possible, a property peculiar to bound variables because of their accepted value as ambiguous words. Thus, when Russell's Theory of Description is used, it reasonable to say that the translation “Someone is the son of someone named Barack and someone named Michelle, and this person does not exist” has meaning and truth without the need to define who the named individuals, for they have already been assigned the value of being “someone,” even if this person does not exist, essentially eliminating the need to recognize unactualized possibilities.