If I put an apple and a tomato in front of you and ask you to find something in common, what is the first thing you would say? There are a variety of similarities between the two objects, but the most common ones are that they are both fruits and they are both red. After this, you would probably walk away wondering why I can’t find similarities between tomatoes and apples.
Regardless of me being able to distinguish tomatoes and apples, there is a philosophical debate on qualities. When you say that an apple is red, ask yourself “What is red?” If red is a color, then what is a color? If color is a property, what is a property? This series of questions and answers will simply go on forever or it will go in circles. People have tried to figure out this question for ages without going in a loop, and so comes the problem of universals.
Universals are what objects, or “particulars” (things which possess but are not qualities) have in common, and these things exist within reality. For example, Plato is a particular. This particular in question, along with Aristotle, are the main philosophers referred to when talking about realism. Realism is essentially the belief in universals.
Plato proposed that there are three components to this: The particular, the quality, and then the “form” of the quality. This form is what Plato considers to be the universal. Basically, you have an apple, you have the apple’s instance of red, and then you have the form of red, which is manifested within apple through the apple’s instance of red. This form is an immaterial thing that exists beyond time and space. This might be confusing, and it is confusing to me, but there’s more to come.
Aristotle proposed that universals are not a form like Plato said. There are only two components, the particular and the quality. The quality itself is the universal. Basically, you have an apple and then you have red. The apple has “red”, or the universal within it. This begs the question of there being differences between the reds in specific objects. For example, if one apple is dark red, and another apple is light red, we can say both apples are red, but those reds may not be the same. Then, how can both qualities be a universal, or the same? Is “red” a universal and then a specific shade of red (denoted by an RGB value) a different universal?
Furthermore, there is an opposing viewpoint to universals called nominalism. I will not cover all of nominalism, but only trope nominalism here. Trope nominalism is essentially taking the concept of universals and dividing them into tropes. If I have an apple, the exact “red” that the apple exhibits is within its own trope. When determining whether an object has the same quality as another, we take the trope of that object and find if it is qualitatively similar to the trope of that object. It eventually turns into a set of tropes, where there is similarities between all the tropes in the set and each trope relates to an object.
To be honest, I don’t properly understand this subject myself. At the very least, I understand that humans separate “particulars” into categories through similarities, but I only see it in a very scientific way. An object is “red” because our brain has specific neurons that send specific electric signals every time it sees a “red” object. It sends visual input that is very similar to another object, and therefore our brain puts them in the same class or category. If I had to pick with one of these ideas, I would have to agree with trope nominalism. While I don’t totally understand it, it seems to go with the scientific way of things. It just seems to relate specific qualities, or sensory input to each other and put them into a set, or category. However, I get that there isn’t a perfect answer, and it’s important to figure this out. Regardless of how important this is to our day-to-day life, when there’s an unanswered question, it’s worth spending time to answer.