BOOK IV.

METAPHYSICS IN THE VARIOUS SCIENCES.

CHAPTER I.

METAPHYSICS IN THE COMMON AFFAIRS OF LIFE.

THE act of breathing does not make us physiologists. Nor does the use of First Principles make us metaphysicians. Just as we all use physiological, so do we also employ metaphysical principles without being conscious of it. Our primitive cognitions, beliefs, and judgments are involved in what we think and do from day to day and from hour to hour, almost from minute to minute of our waking existence.

We assume that we are in space and move in it. We act on the principle that the shortest distance between two points is a straight line. The farmer does not attempt to close in a field by two straight lines. We carry with us a conviction of our personality. We trust our memories and believe in the continuity of time and can find no limit to it. We proceed on the being and identity of objects, especially our personal identity. We are constantly separating parts and combining them into wholes. We delight to discover resemblances and to view things in classes. We are ever comparing the sizes of objects and observing their proportions. We delight to notice the activities of things, and we perceive that they influence us and have power over each other. Whenever we will to take a step in walking or to utter

a sound, we are employing the principle of cause and effect.

Our consciences are constantly guiding and guarding us, in doing this honest and declining this base transaction. When we talk, or when we write, there is a constraint constantly laid upon us by the principle that we should speak the truth. In our money transactions we are bound by the fixed principle of honesty. On seeing a human being in distress, the royal law of love requires that we hasten to relieve him. Our moral nature, following the law of love regulated by law, insists on our constantly showing kindness to our families, our friends, and neighbors.

All this does not show that we are metaphysicians, but it proves that we are constantly exercising qualities which the metaphysician should observe.

CHAPTER II.

THE METAPHYSICS OF PHYSICS.

WE have heard of the man in the French play who was amazed to find that he had been speaking prose all his life without knowing it. I believe that in like manner physicists are constantly using metaphysics without having the least suspicion of it; many of them would indignantly repel the charge, if brought against them.

The physical sciences must ever be conducted in the method of induction, with sense and artificial instruments as the agents of observations. But it has often been remarked that all scientific investigation, indeed all inquiry, if pursued sufficiently far down, conducts into mystery, often into insoluble problems. It will be found that these are the underlying regulative principles which the metaphysician should seek, if not to explain, at least to express. It is not the special business of the physical sciences to inquire into the nature or guarantee of ultimate truths. This work it leaves very properly to metaphysicians, who should be prepared to announce laws of intuition on which the physicist might rest, when he finds himself sinking too far down. They might be more profitably employed in such a work, which lies exclusively in their own province, than in pursuing wild speculative ends, which can never be attained by human

reason.

The powers in nature are so distributed and arranged that they issue in order, in respect of such qualities as space, time, quantity, and energy. To these mathematics can be successfully applied, and they come in with

all their axioms and demonstrations, which are seen to be true at once, as will be shown in a later chapter. Thus both in statics and dynamics, in certain departments of mechanics, astronomy, optics, and thermotics, we come down in the last resort to truths which are beneath physics, and within metaphysics.

Most, if not all, of our intuitive convictions, have a place in the foundation of the deeper physical sciences. Thus the conviction as to the identity of being leads us to chase the substance through the various forms it may assume, and constrains those who are most opposed to hypotheses to speak of ultimate atoms or molecules. The intuition of whole and parts constrains us to look on the abstract as implying the concrete, and prompts us to seek for all the parts which make up the whole. Our intuition as to classes insists that the species make up the genus. Our primitive perceptions as to space make the physicist certain, when he sees a body now in one place, and then in another, that it must have passed through the whole intermediate space. They should prevent him from giving his adherence to the theory that matter consists merely of points of force; the points cannot, properly speaking, be unextended, and there must always be a space between them. Our belief as to time assures us that there can be no break in its flow, and that when we fall in with the same object at two different times, it must have existed the whole intervening period. Our intuitive cognitions of number, quantity, and proportion guide and control us more or less formally in all departments of natural philosophy. Our conviction as to substance and property prompts the physicist, when he discovers a new object, to inquire after its properties, and on perceiving the action of such agencies as magnetism, electricity, and galvanism, to declare that

they must be either separate substances (not probable), or properties of substances. Causation appears in nearly every department of science.

There are sciences which have special primitive truths underlying them. Thus chemistry involves throughout our conviction as to substance and property. There is a class of sciences which proceeds on resemblances and deals with things in classes. They have been called the "Classificatory Sciences" by Whewell, and embrace botany, zoology, and mineralogy so far as it is not a branch of chemistry, and geology so far as it deals with organisms. In all these the mind is guided and guarded by our cognitions in regard to the relations of individuals and classes. Power, force, energy, causation operate in almost all physical sciences, in electric, magnetic, and galvanic action, which all imply power; in geology, as it treats of the forces which have brought the earth's surface to its present state; in physiology which looks at the powers which work in the organism. It is the reigning determinant in mechanics and in the old natural philosophy now called physics.

The physical investigator, engrossed with external facts, and seeking to throw light upon them, will seldom so much as notice these underlying principles, which are unconsciously guiding him, and only on rare occasions will he make a formal appeal to them. Still there will be times when those most prejudiced against metaphysics of every kind will be tempted or compelled to fall back upon them, when diving down into the depths of a deep subject, or when hard pressed by an opponent. It often happens that when they do so, their expression of the principle is awkward and blundering; and I think they have reason to complain of the metaphysician that he has been wasting his ingenuity in unprofitable and un