Universals
Key Figures: Plato, Aristotle, Aquinas, George Berkeley, David Hume, John Locke, Thomas Hobbes, etc.
The discussion of 'universals' can get extraordinarily complex, though the actual concept is fairly easy to understand. Universals are distinguished from particulars: that is, particular things that we see in the world. Examples of a 'particular' would be 'that dog', or St. Augustine, or the lamp that is in the doctor's office at so-and-so. Now, a universals takes all such particulars and groups them together (so to speak). So, a specific [particular] dog, would be an instantiation of 'dog' in general. Likewise, St. Augustine is a particular instance of a 'man', and the universal of a specific lamp is 'lamp'. Hence they are general of all things in particular. However, problems arise: for one, what is the order of hierarchy in existence between particular and universals? Are there particulars first, and then we mentally abstract the universal from it. Or do universals exist first and in some real sense (like Plato thought) and particulars are partaking of the essence of that universal? Certain nominalists, because of problems like these, deny that universals exist in any meaningful, ontological sense. Realists take the opposing view.