Before outlining the modern divisions of Metaphysics we may note that this latter term was not used by Aristotle. We owe it probably to Andronicus of Rhodes († 40 b.c.), who, when arranging a complete edition of Aristotle's works, placed next in order after the Physics, or physical treatises, all the parts and fragments of the master's works bearing upon the immutable and immaterial object of the philosophia prima; these he labelled τὰ μετὰ τὰ (βιβλία) φυσικα, post physica, the books after the physics: hence the name metaphysics,[21] applied to this highest section of speculative philosophy. It was soon noticed that the term, thus fortuitously applied to such investigations, conveyed a very appropriate description of their scope and character if interpreted in the sense of “supra-physica,” or “trans-physica”: inasmuch [pg 018] as the object of these investigations is a hyperphysical object, an object that is either positively and really, or negatively and by abstraction, beyond the material conditions of quantity and change. St. Thomas combines both meanings of the term when he says that the study of its subject-matter comes naturally after the study of physics, and that we naturally pass from the study of the sensible to that of the suprasensible.[22]
The term philosophia prima has now only an historical interest; and the term theology, used without qualification, is now generally understood to signify supernatural theology.
VI. Departments of Metaphysics: Cosmology, Psychology, and Natural Theology.—Nowadays the term Metaphysics is understood as synonymous with speculative philosophy: the investigation of the being, nature, or essence, and essential attributes of the realities which are also studied in the various special sciences: the search for the ultimate grounds, reasons and causes of these realities, of which the proximate explanations are sought in the special sciences. We have seen that it has for its special object that most abstract aspect of reality whereby the latter is conceived as changeless and immaterial; and we have seen that a being may have these attributes either by mental abstraction merely, or in actual reality. In other words the philosophical study of things that are really material not only suggests the possibility, but establishes the actual existence, of a Being that is really changeless and immaterial: so that metaphysics in all its amplitude would be the philosophical science of things that are negatively (by abstraction) or positively (in reality) immaterial. This distinction suggests a division of metaphysics into general and special metaphysics. The former would be the philosophical study of all being, considered by mental abstraction as immaterial; the latter would be the philosophical study of the really and positively changeless and immaterial Being,—God. The former would naturally fall into two great branches: the study of inanimate nature and the study of living things, Cosmology and Psychology; while special metaphysics, the philosophical study of the Divine Being, would constitute Natural Theology. These three departments, one of special metaphysics and two of general metaphysics, would not [pg 019] be three distinct philosophical sciences, but three departments of the one speculative philosophical science. The standpoint would be the same in all three sections, viz. being considered as static and immaterial by mental abstraction: for whatever positive knowledge we can reach about being that is really immaterial can be reached only through concepts derived from material being and applied analogically to immaterial being.
Cosmology and Psychology divide between them the whole domain of man's immediate experience. Cosmology, utilizing not only the data of direct experience, but also the conclusions established by the analytic study of these data in the physical sciences, explores the origin, nature, and destiny of the material universe. Some philosophers include among the data of Cosmology all the phenomena of vegetative life, reserving sentient and rational life for Psychology; others include even sentient life in Cosmology, reserving the study of human life for Psychology, or, as they would call it, Anthropology.[23] The mere matter of location is of secondary importance. Seeing, however, that man embodies in himself all three forms of life, vegetative, sentient, and rational, all three would perhaps more naturally belong to Psychology, which would be the philosophical study of life in all its manifestations (ψυχή, the vital principle, the soul). Just as the conclusions of the physical sciences are the data of Cosmology, so the conclusions of the natural or biological sciences—Zoology, Botany, Physiology, Morphology, Cellular Biology, etc.—are the data of Psychology. Indeed in Psychology itself—especially in more recent years—it is possible to distinguish a positive, analytic, empirical study of the phenomena of consciousness, a study which would rank rather as a special than as an ultimate or philosophical science; and a synthetic, rational study of the results of this analysis, a study which would be strictly philosophical in character. This would have for its object to determine the origin, nature and destiny of living things in general and of man himself in particular. It would inquire into the nature and essential properties of living matter, into the nature of the subject of conscious states, into the operations and faculties of the human mind, into the nature of the human soul and its mode of union with the body, into the rationality of the human [pg 020] intellect and the freedom of the human will, the spirituality and immortality of the human soul, etc.
But since the human mind itself is the natural instrument whereby man acquires all his knowledge, it will be at once apparent that the study of the phenomenon of knowledge itself, of the cognitive activity of the mind, can be studied, and must be studied, not merely as a natural phenomenon of the mind, but from the point of view of its special significance as representative of objects other than itself, from the point of view of its validity or invalidity, its truth or falsity, and with the special aim of determining the scope and limitations and conditions of its objective validity. We have already referred to the study of human knowledge from this standpoint, in connexion with what was said above concerning Logic. It has a close kinship with Logic on the one hand, and with Psychology on the other; and nowadays it forms a distinct branch of speculative Philosophy under the title of Criteriology, Epistemology, or the Theory of Knowledge.
Arising out of the data of our direct experience, external and internal, as studied in the philosophical departments just outlined, we find a variety of evidences all pointing beyond the domain of this direct experience to the supreme conclusion that there exists of necessity, distinct from this directly experienced universe, as its Creator, Conserver, and Ruler, its First Beginning and its Last End, its Alpha and Omega, One Divine and Infinite Being, the Deity. The existence and attributes of the Deity, and the relations of man and the universe to the Deity, form the subject-matter of Natural Theology.
VII. Departments of Metaphysics: Ontology and Epistemology.—According to the Aristotelian and scholastic conception speculative philosophy would utilize as data the conclusions of the special sciences—physical, biological, and human. It would try to reach a deeper explanation of their data by synthesizing these under the wider aspects of change, quantity, and being, thus bringing to light the ultimate causes, reasons, and explanatory principles of things. This whole study would naturally fall into two great branches: General Metaphysics (Cosmology and Psychology), which would study things exempt from quantity and change not really but only by mental abstraction; and Special Metaphysics (Natural Theology), which would study the positively immaterial and immutable Being of the Deity.
This division of Metaphysics, thoroughly sound in principle, [pg 021] and based on a sane and rational view of the relation between the special sciences and philosophy, has been almost entirely[24] supplanted in modern times by a division which, abstracting from the erroneous attitude that prompted it in the first instance, has much to recommend it from the standpoint of practical convenience of treatment. The modern division was introduced by Wolff (1679-1755), a German philosopher,—a disciple of Leibniz (1646-1716) and forerunner of Kant (1724-1804).[25] Influenced by the excessively deductive method of Leibniz' philosophy, which he sought to systematize and to popularize, he wrongly conceived the metaphysical study of reality as something wholly apart and separate from the inductive investigation of this same reality in the positive sciences. It comprised the study of the most fundamental and essential principles of being, considered in themselves; and the deductive application of these principles to the three great domains of actual reality, the corporeal universe, the human soul, and God. The study of the first principles of being in themselves would constitute General Metaphysics, or Ontology (ὄντος-λόγος). Their applications would constitute three great departments of Special Metaphysics: Cosmology, which he described as “transcendental” in opposition to the experimental physical sciences; Psychology, which he termed “rational” in opposition to the empirical biological sciences; and finally Natural Theology, which he entitled Theodicy (Θεός-δίκη-δικαιόω), using a term invented by Leibniz for his essays in vindication of the wisdom and justice of Divine Providence notwithstanding the evils of the universe.
“The spirit that animated this arrangement of the departments of metaphysics,” writes Mercier, “was unsound in theory and unfortunate in tendency. It stereotyped for centuries a disastrous divorce between philosophy and the [pg 022] sciences, a divorce that had its origin in circumstances peculiar to the intellectual atmosphere of the early eighteenth century. As a result of it there was soon no common language or understanding between scientists and philosophers. The terms which expressed the most fundamental ideas—matter, substance, movement, cause, force, energy, and such like—were taken in different senses in science and in philosophy. Hence misunderstandings, aggravated by a growing mutual distrust and hostility, until finally people came to believe that scientific and metaphysical preoccupations were incompatible if not positively opposed to each other.”[26]
How very different from the disintegrating conception here criticized is the traditional Aristotelian and scholastic conception of the complementary functions of philosophy and the sciences in unifying human knowledge: a conception thus eloquently expressed by Newman in his Idea of a University:—[27]