Classification of the Sciences and Divisions of Philosophy

The Philosophical System of Thomas Aquinas, by Maurice de Wulf, edited and adapted for the web by Jonathan Dolhenty

XVIII. Classification of the Sciences and Divisions of Philosophy

A. Particular and General Sciences

At the time of the thirteenth century, the West possessed a comprehensive classification of the sciences, which we may well look upon as one of the characteristic achievement of the mediaeval mind, and which, in its main features, lasted up to the time of Wolf.

At the lowest stage we find the particular sciences, — which for the Schoolmen were the same as the experimental sciences. Such are Astronomy, Botany, Zoology, Human Physiology, Medicine, also Civil and Canon Law, which became separate and autonomous sciences in the twelfth century.

They derive their particularity:

(a) From the material object, which is particular. They are concerned only with a restricted section of the corporeal world. Botany, for instance, has nothing to do with economic wealth.
(b) From their formal object, which, in consequence of what we have just said, cannot be grasped or abstracted from all reality, but only from a more or less restricted section of it.
But the detailed study of the sensible world by sections does not satisfy the mind. After the details, we seek for a comprehensive view of the whole, and this can only be furnished by philosophy. The man of science is like a stranger who explores a city bit by bit, and walks through the streets, avenues, parks, museums and buildings one after another. When at length he has wandered over the city in all directions, there still remains another way of becoming acquainted with it: from the top of a tower, the city would present to him another aspect, — its divisions, its general plan, and the relative disposition of its parts. The philosopher is just such a man: he views the world from above as it were, and tries to realize its general structure, for philosophy is a generalized knowledge of things, a synthetic view of that material world of which alone we have direct and proper knowledge, and then by extension, of all that is or can be (III, B). It is human wisdom (sapientia), science par excellence. This general science or philosophy constitutes the second stage of knowledge.

In contrast to the particular sciences, philosophy derives its generality,

(a) From its material object, — which is all that exists or can exist. The man who takes in, by a single glance, the whole of a city from the top of his tower does not exclude any part from his regard, but he only looks for the general aspect of the whole, that which belongs to all and not merely to some of its parts. In the same way philosophy, instead of dealing with only one department of reality, takes in all the real.
(b) From its formal object which consists of points of view that affect and are found in all reality. Indeed these comprehensive views are possible only because the mind seizes in the immensity of reality certain aspects which are present everywhere and in everything, and which in consequence belong to the very essence of reality. Philosophy is defined as the investigation of all things by means of that which is fundamental in them and common to all. Sapientia est scientia quae considerat primas et universales causas [1].
In other words, philosophy is a science which coordinates or makes a synthesis, for the materials it studies and the point of view from which it studies them are both characterized by generality. What are these general and comprehensive points of view or aspects which the human mind discovers in its study of the universe? This question brings us to the division of philosophy.

B. Division of Philosophy

Starting from a well-known classification of Aristotle, Thomas remarks that philosophical sciences admit of a first subdivision into theoretical and practical. The human mind (for all science, as we have seen, is a work of the mind) can come into contact with the real in general, or, as it was then called, the ‘universal order,’ in two ways. In the first place we may study this universal order such as it is in and for itself, and look for its general features, without subordinating this knowledge to ourselves. This constitutes a speculative or theoretic philosophy, the end of which is knowledge for its own sake. Or, in the second place one may study the universal order of things not as such, but in so far as it enters into relation with our conscious life (knowing, willing, producing). It is in this sense that this part of philosophy is called practical.

Each of these two groups admits of further subdivision. Speculative philosophy comprises Physics (in the Aristotelian sense) [2], Mathematics, Metaphysics. Practical philosophy includes Logic, Moral Philosophy, Esthetics. Let us consider these various classifications in the light of the scholastic teaching concerning the construction of the sciences.

C. Speculative Philosophy

The division of speculative philosophy into Physics, Mathematics, Metaphysics does not correspond to three separate sections of being in the universe [3], but results from the varying profundity of point of view or degree of abstraction with which we study the totality of things. Physics, mathematics, and metaphysics, all study the material universe as a whole, but each studies a particular aspect of all reality, change, quantity, and being, respectively.

(a) Physics. Everything is carried along on the stream of change, which the Schoolmen called motus (from moveri). The study of change in its inmost nature and its implications is the first step in a general understanding of the universe. It is the task which belongs to Physics or to the philosophy of nature. Since man forms part of the world of sense reality, psychology is a department of physics, and the epistemological inquiry belongs to psychology.

(b) Mathematics. But there is in the sensible universe something more profound than change, — namely, quantity. For every change is closely bound up with conditions of time and space in which the change takes place, while quantity, on the contrary, as studied in numbers and geometric figures, is grasped apart from the sensible condition of real quantified beings. Mathematics, which studies quantity and its implications, is for the Schoolmen a general and therefore a philosophical science, — a conception to which contemporary mathematicians tend to return.

(c) Metaphysics. Lastly, beyond change and quantity, metaphysics seizes in the things of experience the most profound aspects of reality, the strata which underlie all the others: being and the general determinations of being such as essence, existence, substance, unity, goodness, action, totality, causality, etc. These most general aspects of reality themselves constitute a synthetic view of the material universe. But while change, which implies duration in time, and while quantity, which is the primary attribute of bodies, depends on the material state of the universe, this state is not essential to the notion of being or those other ideas which are correlative to it. If there should be suprasensible beings, such as God, or the soul, then these metaphysical notions would be applicable to them, with certain necessary corrections. In this way natural theology and the non-experimental part of scholastic psychology really form part of metaphysics.

D. Practical Philosophy

Practical philosophy is equally general in character, since through our conscious powers of knowing, willing, and producing we enter into relation with all reality. This general category includes logic, moral philosophy or ethics, and the philosophy of art or esthetics. Logic draws up a scheme of all that we know, and the method of constructing the sciences; as there is nothing that the human mind cannot know in some imperfect way, logic is a general science. Ethics, again, studies the realm of human conduct, and there is nothing in human life that cannot become the subject of morality. It is to be noted that politics and domestic ethics are, like individual ethics, merely applications of general moral philosophy. The philosophy of art deals with the order achieved by man externally through the guidance of reason, as when, for example, “he builds a house, or makes a piece of furniture.” Philosophy of art here includes the study of the mechanical as well as the fine arts.

It is easy to realize that we have adopted this philosophical classification in the preceding parts of this work [4].

Particular sciences precede philosophy, and the latter must be in a sense based upon them. The programme of the Faculty of Arts in the Universities of Paris and Oxford was inspired by this principle. The arrangement by which the particular sciences form the threshold of philosophy gives to the latter an experimental basis, or, as we should say today, a scientific foundation. General views presuppose particular or detailed one to a certain extent.

(Editor’s Note: Detailed diagrams of the Aristotelian, Thomistic, Wolffian, and Dolhenty classifications of philosophy are available on this website at Diagram: Divisions of Philosophy.)



  1. In Metaph., I, lect. 2.

  2. From the Greek word for nature. Not to be confused with “Physics” in the modern sense, which is a particular science.

  3. As in the division introduced by Wolf, for whom speculative philosophy concerns itself with (a) nature other than man, i.e., Cosmology, (b) man, (Psychology), (c) God, i.e., Natural Theology or Theodicy. Wolf reserves the name Metaphysics for considerations common to all three groups. For a chart describing the Wolffian division, see Diagram: Divisions of Philosophy in the Adventures of Philosophy section.

  4. As for mathematics, and the controversies of the thirteenth century concerning numbers, quantity, mathematical infinity, and so on, a clear understanding of these questions is not essential to our present aim, and we therefore pass over them in silence. It will be noticed that in the above classification the philosophy of art is placed in the group of practical sciences. We might, however, regard it instead as a third and separate group, corresponding to the poetical sciences of Aristotle.

The late Dr. Jonathan Dolhenty was the Founder and President of The Center for Applied Philosophy and the Radical Academy, and is Honorary Philosophy Editor at The Moral Liberal. The Moral Liberal has adopted these projects beginning with a republishing and preserving of all of Dr. Dolhenty’s work.