I have shown that when one fact is about a genus and another fact is about a species of that genus, the fact about the genus is higher than that about the species. But there are multiple ultimate categories. The highest category is substance, and knowledge about substance is the highest form of knowledge.
There are a number of ultimate categories: substance, number, quality and time among others. Nothing within these categories can be reduced to any other category. But this does not mean that all of these categories are equal in regards to knowledge. If one of these categories depends on another, then knowledge of one of them will also depend on the other.
All of the categories are about some aspects of things. They are either accidents, properties, tropes or substances. Now tropes are particular instances of accidents or properties. Therefore, knowledge of tropes is dependent on knowledge of properties and accidents. Both properties and accidents are properties and accidents of particular things. Not only this, but the particular properties and accidents that exist do so because of the kind of thing that it is. For example, dogs have hair. Reptiles don’t. The reason that dogs have hair has to do with the kind of animal they are.
There is one further consideration. If we claim that an animal exists, or that Barack Obama exists, nothing further needs to be said. However, we cannot simply claim that whiteness exists or that three meters exists. Whiteness and three meters cannot exist on their own. In order for something to be white, some substance must be white. It is the same with three meters. It is the same way with any property or accident. They cannot exist on their own. Since they cannot, they must always be described as a particular way that a substance exists. So whiteness exists because the substance that is white reflects light equally in the visible spectrum. This means that we need to have some understanding of the substance in order to fully understand what white is.
It is for this reason that knowledge of substance is the highest knowledge of all. Substance is an ultimate genus, but since knowledge of substance is required to fully understand any other genus, knowledge of substance is higher than knowledge of any other genus. Furthermore, knowledge of the genus of a thing is higher than knowledge of a species of it. Since knowledge is only disunified if it has a different subject. This means that the highest knowledge of all knowledge is knowledge of substance in general.
The study of substance itself is the highest form of knowledge. This study is what Aristotle referred to as philosophy. However, there is knowledge about other things is still possible. We all consider various ordered studies of a subject to be possible. These include science, history, construction work and dentistry. These various subjects must all be unified in some way. How they are unified in the subject of my next post in this series.