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.

Notes:
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.