Some authors, in past centuries, thought that the only object of metaphysics was to treat of beings above nature; and accordingly taught that God and the angels alone were metaphysical beings—that is, beings ranging above nature. On the contrary, man and this visible world—that is, all creatures liable to local motion—they called natural beings, and considered them to be the proper and exclusive object of physical science. This view was grounded, apparently, on the latent assumption that metaphysics meant above physics; which, however, is not correct, as μετὰ does not mean above, but after; and therefore metaphysical is not synonymous with supernatural.[89] On the other hand, God and the angels are undoubtedly physical beings; for they are complete beings, having their complete physical nature and their separate existence. We cannot call them metaphysical beings; for we know of no beings which deserve the name of metaphysical but those incomplete entities which are attained through the intellectual analysis of physical and complete beings.
As to man and all the other natural things, every one will see that though they are, in one respect, the proper object of physics, yet they are also, in another respect, the proper object of metaphysics; and this too, without in the least confounding the two branches of knowledge. The attributions of physics and of metaphysics are, in fact, so distinct that there can be no danger of the one invading the province of the other, even though they deal with the same subject. The office of the physicist is to investigate natural facts, to discuss them, to make a just estimate of them, and to discover the laws presiding over their production. This, and no other, is the object of physics, to accomplish which it is not necessary to know the essence of natural things. Hence, the physicist, after ascertaining the phenomena of nature and their laws, cannot go further in his capacity of physicist. But where he ends his work, just there the metaphysician begins; for his office is to take those facts and laws as a ground for his speculations in order to discover the essential principles involved in the constitution of natural causes, and to account by such principles for all the attributes and properties of things. This is the duty of the metaphysician. Thus natural things, although an object of physics when considered as following certain laws of action or of movement, are nevertheless an object of metaphysics when considered in their being and intimate constitution.
On this point even physicists agree. "Instead of regarding the proper object of physical science as a search after essential causes," says one of the best modern champions of scientific progress, "it ought to be, and must be, a search after facts and relations."[90] Hence, physical science deals with natural facts and their relations exclusively; the search after causes and essential principles constitutes the object of a higher science; and such a science is real philosophy, or metaphysics proper.
I was surprised at finding in Webster's English Dictionary (v. Metaphysics) the following words:
"The natural division of things that exist is into body and mind, things material and immaterial. The former belong to physics, and the latter to the science of metaphysics." From what we have just said, it is clear that this division is not accurate. We must add that it is not consistent with the definition of metaphysics given by the same author only a few lines before. Metaphysics, says he, is "the science of the principles and causes of all things existing." Now, if material things existing do not belong to metaphysics, it evidently follows that either material things existing have no principles and no causes, or that such principles and causes are no object of science. But it is obvious that neither conclusion can be admitted. Furthermore, it is well known that all metaphysicians treat of the constitution of bodies—a fact which conclusively proves that material things are not excluded from the object of metaphysics.
Here, however, we must observe that some modern writers, while conceding this last point, contend that material things must be mentally freed from their materiality before they can be considered as an object of metaphysics. Their reason is, that this science is concerned with real things only inasmuch as they consist of principles known to the intellect alone. Matter, they say, is not an object of the intellect. Therefore, the object of metaphysics must be immaterial—that is, either a thing which has no matter of its own, or at least a thing which is conceived, through mental abstraction, as free from matter.
But we should remember that, according to the common doctrine, the true and adequate object of metaphysics is all real being as such, whether it be material or immaterial; and that it is, therefore, the duty of the metaphysician to divide substance into material and immaterial, and to give the definition of both; for it belongs to each science to point out and define the parts of its own object. Hence, the metaphysician is bound to explain how things material differ from things immaterial, and has to ascertain what metaphysical predicates are attributable to material substance on account of its very materiality.[91] Now, it is evident that nothing of the kind can ever be done by a philosopher who, through mental abstraction, considers material substance as freed from its matter. For when, by such an abstraction, he has taken away the matter, what else can he look upon as a ground of distinction between material and immaterial beings? We must admit, then, that material things, inasmuch as they are real things, and only in that manner in which they are real (that is, with their own matter), are a proper object of metaphysics.
To the patrons of the opposite view we confidently answer that their argument has no sound foundation; for though it is true that no material thing, owing to the complexity of its simultaneous actions on our senses, distinctly reveals to us its material constitution, yet it is not true that material things cannot be understood by our intellect unless they are mentally stripped of their matter. To understand them thus would be simply to misunderstand them. Matter and form are the essential constituents of material substance, as all metaphysicians admit; it is, therefore, impossible to understand the essence of material substance, unless the intellect reaches the matter as well as the form.[92] Let us add that those very authors who in theory affect to exclude matter from the object of metaphysics find it impossible to do away with it in practice, and, in spite of the theory, devote to matter, as such, a great number of pages in their own metaphysical treatises.
Thus far we have defined the object of metaphysics. We now come to its method, on account of which it is so frequently assailed by the votaries of experimental science. Metaphysics, they say, is a science à priori; it is, therefore, altogether incompetent to decide any matters of fact; and, if so, what is the use of metaphysics? To this reasoning, which claims no credit for perspicacity, many answers can be given.
And first let us suppose for a moment that metaphysics is a science altogether à priori. Does it follow that it has no claim to our most careful attention? Geometry, algebra, and all pure mathematics are à priori sciences. Are they despised on this account? We see, on the contrary, that for this very reason they are held in greater honor and lauded as the most thorough, the most exact, and the most irrefragable of all sciences. Some will say that the object of mathematics is not to establish natural facts, but only relations; but this is equally true of metaphysics. The metaphysician, when treating of physical subjects, assumes the facts and laws of nature as they are presented to him by the physicist; he has not to establish them anew, but only to account for them by showing the reason of their being. Metaphysics would, therefore, be as good, as excellent, and as interesting as geometry, even if it were an à priori science.