Philosophy, the love of wisdom, can in practice be divided into useful categories, so that each can be studied separately. In the end, we want to view reality as a unified whole (after all, what is the “universe” if not a unified concept of reality?). Still, we do well to analyze, to break down knowledge and understand its parts.
After studying logic, which is more of a preparation and ordering of the mind toward the study of philosophy than a part of philosophy itself, we can look at two general branches of philosophy: Practical and Speculative.
Practical philosophy aims at action, for the sake of conduct or operation. It is not merely knowledge for its own sake, but links “is” with “ought.” The truths we derive from it are not “complete” until put into action, until we “do” these truths. Major branches of practical philosophy include the arts of “doing” which are ethics, economics, and politics, but may also include arts of “making” such as the fine arts.
In speculative philosophy, we seek knowledge for its own sake. It is divided into three parts, and these depend directly on their relation to matter. The most abstract is metaphysics, mathematics is an intermediate knowledge, and natural philosophy (known simply as physics in older usage) is directly related to matter.
We will here focus on the latter three, the speculative sciences, and seek to better understand these levels of abstraction. To do so, we must understand abstraction, and see how it is related to but different from separation.
All three of these sciences have there origin in sense knowledge. They therefore start with sensible objects, and this means material being. In the study of natural philosophy, therefore, we merely abstract the universal from the particular. We study the features of flesh and bones, apart from this particular flesh or this particular bone. This is to consider objects as they contain common sensible matter, which is to say that we are considering matter as such, such as flesh and bones, but not particular matter, such as “this flesh” and “these bones,” because our interest is in what “flesh and bones” do, and not what some particular set of flesh and bones do. We do not imply however, that flesh or bones actually exist apart from particular flesh and particular bones.
St. Thomas proposes that we use “to abstract” or “abstraction” in a narrow sense to cover only cases where we think apart things which do not exist apart, when from AB, I abstract A without suggesting that A exists apart from AB (McInerny, Metaphysics Lecture). So A here can represent “flesh,” and B is the particular flesh that we study. We need not imply that flesh exists apart from particular flesh to study flesh. We can ponder A, then, apart from B, without implying that A ever actually exists apart from B. Thus, whenever we define flesh, we do not define “this flesh,” but rather, flesh in general. In doing so, we still must include matter in the definition, because matter is a part of what it is to be “flesh.”
Freedom from all sensible matter, including in the definition of what is studied, brings us to mathematics. For we do not need to include matter in the definition of a circle as we do when we define flesh. However, there are no existing circles apart from matter. We see that the difference, then, is that while both require matter to exist, mathematical objects do not require that matter be part of their very definition. This comprises the major difference in how we understand math as the second level of abstraction.
Metaphysics goes beyond this by not only abstracting the object of study from sensible matter, but understanding that some things can exist and be defined apart from any matter whatsoever. In other words, this subject is attained by an abstraction of the third order properly called a separation, whereby the mind leaves aside all the limitations of matter and cognizes an object that is intelligible without reference to matter and so is independent of matter in both meaning and existence. (Elements of Philosophy) Separation in the narrow sense is taken to characterize metaphysics. In the narrow sense, separation is the consideration of A without B when A exists apart from B. (McInerny)
When we look at God, whose existence is already proven in natural philosophy, we see one such immaterial being. We also see, in psychology, the existence of our soul, which can exist apart from matter and, although defined by it as the form of the body, is a substantial form and can exist on its own, apart from the material body. These are basic examples of how we arrive at this level of abstraction and see that things do truly exist so that metaphysics as a separate branch of study is a legitimate endeavor.
In brief, the differentiation of the sciences comes about by the different ways of demonstrating properties of these objects. This distinction does not (necessarily) arise because of the different objects studied, but from the diversity of principles that can be found in the objects of study. In logic, definition come about through “middle terms,” and the middle terms of the three speculative sciences we have looked at are arrived at precisely by the type or level of abstraction used.
The use of analogy in the study of metaphysics is relevant here. Analogy is a kind of predication midway between univocation and equivocation. This is necessary primarily because “being” cannot be a genus, for if being were a genus, substance and accidents would have to differ in something other than “being.” Therefore, recognizing this difference, but knowing it cannot be other than within being, we realize that we must use being analogously when speaking of different modes of being. This is important here, for analogous terms are so called by the fact that they arise by a sort of incomplete abstraction (separation), whereas univocal terms arise from complete abstraction.
Therefore, it is by a sort of incomplete abstraction from one subject that we understand such terms as goodness and even being itself. The primary subject that we abstract these analogies from is being itself, which is God. For example, God is not [merely] “good” but is goodness itself, whereas other things are “good” by way of analogy, and this goodness is understood as related to God’s goodness but not univocal to it.
The understanding of abstraction and separation, then, are not only important for understanding the difference in the speculative sciences, but in understanding metaphysical topics. It is especially important in contemplating how all created things relate to God without falling into the areas of thinking that God’s being and our being, for example, are completely univocal (e.g. Scotus) or completely equivocal (Maimonides?).
What makes us rational animals, different as human from all other animals, is our ability to abstract the universal from the particular, and to seek higher things. We are, by nature, made to learn from the sensible material things around us, but to know things beyond them, and this by abstraction. We are, as has been often said, a microcosm, the link between the spiritual and the material world, being the one unique creature that we know of to participate in both. We are made to know being, and in the end, Being Himself.