It doesn't take long before scrolling through them all in one long list becomes impractical. When this happens, it's almost certainly time for categorical logic to come to the rescue. When you organize your files on a computer into folders or directories, assuming you are not just randomly dumping them into any old folder or directory, you are applying techniques of categorical logic to make decisions of what goes where. You might, for example, decide that all graphics images should have a place of their own, apart from letters you write, financial files, etc. As a result of studying categorical logic, the organization of files in your computer could become noticeably more efficient.
Categorical logic is useful in a variety of ways.
Categorical reasoning of varying levels of complexity shows up commonly in both academic pursuits and everyday business. Human beings, for example, are a species within the larger category of primates, which all belong to the still larger category of mammals, which in turn belong to the yet larger category of organisms with a backbone, etc. As those who are familiar with the field of taxonomy know well, classification decisions in biology can depend upon some very subtle argumentation. Most of the logical work of taxonomy occurs in the form of deductions that are essentially like those we will be working with in this unit. The extended debates about classification that have occurred among biologists over the past two centuries are testimony not only to the complexity of categorical problems, but also to the durability of the logic that structures these discussions.