In my last two posts, I have explored the nature of the productive and active sciences. The last science is theoretical science. This is the science that exists entirely for the sake of knowledge. There are a finite number of theoretical sciences and they can be categorized. They are theology, philosophy, mathematics, natural science, psychology, sociology and history.
A theoretical science is defined by what it chooses to study and how it chooses to study it. So if there are a finite number of topics to study, then there will be a finite number of theoretical sciences. The only way to determine whether or not there are a finite number of science is just by attempting to divide the possible sciences. If we divide the sciences by contradictories, then there is no possibility of future information overturning our understanding. As long as we choose the most essential features we will be sure to divide theoretical knowledge correctly.
The first way to divide theoretical knowledge is by how that knowledge is obtained. Either that knowledge is obtained by demonstration or it is not. Demonstration is a form of deduction that begins with the knowledge we have through our senses. If that knowledge is not obtained by demonstration, then that knowledge cannot be of any secondary substance, property or accident. Therefore, such a science would either have to a science of individuals or a science of existence since there is no sense of speaking of a science of an individual or a trope. A science of existence could not be understood by reasoning. Therefore, if there were such a science then we would have to have the knowledge from existence itself. Such a science must begin by claiming that existence itself has given us that knowledge – and such a science is known as theology. A science of individuals would explain individual human acts, beliefs and practices by showing how these influenced each other and why they did so. Such a science would be called history.
All of the other sciences are obtained by demonstration – and are therefore of substances, properties or accidents. The highest of these sciences is philosophy – the science of substance itself. Now substance can be divided into material and immaterial substance. Material substance can undergo substantial change. The study of material substance as such is known as natural science. Some material substances are alive – they have a principle of activity inside their own essence that is directed at their own essence. This feature of living things gives rise to sensation in animals and rationality in human beings. The study of these things – as activity – is the domain of psychology. Finally, we as rational substances (human beings) can make artifacts both material and immaterial. The study of these artifacts is a part of psychology or it is called sociology.
These last divisions have completely divided substance into various categories. All that remains is properties and accidents. The study of quantity as such is mathematics. All other properties or accidents may be understood by the previous sciences. In order to show that these divisions are all that is needed, we would need to demonstrate this will all currently recognized disciplines. Before that, I will mention how knowledge is to be understood.