Categories

Even though categories play an important role in philosophy (especially in ontology and metaphysics), it is clear that not all categories play such a role. Philosophers are very interested in the categories of the material and the mental, or the abstract and the concrete, but not so much in the categories of knives and forks, or fruit and vegetables. This fact instantly raises the first philosophical problem connected with categories: what is the difference between those that seem philosophically weighty, and those that do not? Once we have addressed this question and demarcated the categories philosophers are interested in (sometimes referred to as ontological categories), an immediately following question concerns their nature. Does the set of these categories (often a set that is structured in some way, frequently in the form of a tree) constitute the structure of the world in a very general sense, or is this set rather indicative of the structure of our thinking about the world? In either case it is necessary to come up with some idea of how we can know the ontological categories in the first place. We can find out about knives and forks by merely looking at the world, but the fundamental distinction between concrete things like billiard balls and abstract things like numbers is not similarly obvious. We therefore need to engage in some epistemology of metaphysics in order to determine whether we find out about the structure of categories by examining the world through our senses, by various armchair exercises (such as reflecting on our thinking about the world, or about the use of language), or by a combination of the two. Finally, we may also wonder what our newly acquired knowledge of categories could be for. What role do ontological categories play in solving philosophical problems, or in formulating philosophical theories? And is their usefulness strictly confined to philosophy, or do they have any function in other intellectual endeavours?