CHAPTER V1

REASONING.

SECTION I.

THE NATURE AND OBJECT OF REASONING,

AND THE MANNER IN WHICH IT PROCEEDS.

WE now come to the consideration of that series of mental acts denominated reasoning. Before, however, we enter upon this branch of our subject, it may be useful to review again, very briefly, the ground which we have gone over, that we may distinctly perceive the point from which we proceed, and learn the relation which this form of mental action holds to the other acts of the mind.

By our perceptive powers, we become acquainted with the qualities of external objects, and, in general, with the facts in the external world. By our consciousness, we learn the facts existing in the world within us. By original suggestion, various intuitive truths and relations become objects of cognition. By abstraction, conceptions of individuals assume the form of general ideas; and by memory, all this knowledge is retained and recalled to our consciousness at the command of the will.

Were we endowed with no other powers than these, we might enjoy the pleasures of knowledge. Whatever we had observed or experienced, and whatever had been observed and experienced by others, might be retained, generalized and combined, and thus our acquisitions might be both ex

tensive and valuable. But, with no other faculties, we could only know what we or other men had actually observed or experienced. We could never make use of this knowledge to penetrate into the unknown. In a word, we could observe, and feel, and generalize, and classify, and remember, but we could not reason.

But such is not the condition of the human mind. As soon as we acquire any knowledge whatever, we are prompted to use it for the purpose of acquiring other knowledge. We are continually saying to ourselves, if this be thus, then this other must be so; or this must be so, because this and that are so. If this be so, what must of necessity follow? This is the language of human beings, young and old, savage and civilized, learned and ignorant. It is the impulse of our common nature, and one of the endowments with which we have been blessed by a merciful Creator. He has enabled us to cognize relations existing between certain truths, from which emanate other truths different from the preceding, but which, without a knowledge of them, could never have been discovered.

The results of the exercise of this faculty have been most astonishing. Unlike our other endowments, every one of its acts provides a wider field for its future employment, and thus its range is absolutely illimitable. The perception of one color gives me no additional power to perceive another color. A fact remembered furnishes only accidentally a basis or an aid to wider recollection. But every truth discovered by the reasoning power, and, in fact, every truth, however acquired, becomes, by use of this power, the means for proceeding to further discovery. Through the elementary cognitions in geometry, our reason at first discovers certain truths concerning lines, angles and triangles. Using these increased means of knowledge, it proceeds to discover truths concerning circles and squares; and, using

these again, it discovers those concerning solids, spheres and spherical triangles; and, using these again, it has been able to reveal to us the magnitude, distances and motions, of the heavenly bodies, and thus unfold the wonders of modern astronomy. The knowledge which we thus obtain is original knowledge; that is, it is given us specially by this faculty, and could be given us by no other. How could we ever learn the distance or magnitude or motion of the planets, either by perception, or consciousness, or original suggestion, or abstraction, or memory? The same remark is true respecting the other sciences. Every science which presents to us knowledge which could not be attained by the powers above mentioned, must rely for its discoveries wholly on reasoning.

We see, then, the nature of this faculty. It cognizes nothing directly and immediately. It neither perceives the facts of the outward nor is conscious of the facts of the inward world; it furnishes no original suggestions, and neither abstracts nor remembers; but it receives these data as they are delivered to it by these preceding faculties, and, by a process of its own, uses them to discover new truths, to which none of them could ever have attained. The manner in which this is done, we shall attempt to explain.

Reasoning consists in a series of mental acts, by which we show such a relation to exist between the known and the unknown, that if the former be true, the latter must also be equally true. Thus, in geometry, the known with which we commence is the definitions and axioms. Our first demonstration shows such relations to exist between them and the first proposition, that if those be true this must be true. also. This first proposition is thus added to the known, and becomes as firm a ground from which to reason as the definitions and axioms from which we at first proceeded. In our next step we again show, by our reasoning powers, that

if this increased known be true, the second proposition must be true also. We then add our second proposition to the known, and with this increased material of knowledge proceed to the third proposition; and so on continually. In each act of reasoning, we observe first the known, reaching to a definite limit, beyond which all is uncertainty. We observe, secondly, a proposition in the unknown which may be true or may be false, of which nothing can with certainty be affirmed, separated from the known by a chasm, so to speak, of thus far impassable ignorance. The reasoning power projects a bridge across this chasm, uniting them indissolubly together, transforming the unknown into the known, adding a new domain to science, and enlarging by every such act the area of human knowledge.

If such be the nature of the mental process which we denominate reasoning, it suggests to us three distinct topics for consideration:

First, the nature of the truths from which we proceed. Secondly, the validity of the results at which we arrive. Thirdly, the nature of the process by which we pass

from the one to the other.

To the consideration of these subjects the remainder of this section will be devoted.

I. The nature of the truths from which we proceed.

I have already said that, in reasoning, we design to show that if certain things are true, certain other things, whose truth is now unknown, must be true also. We then must, of necessity, proceed from the true to the doubtful, from the known to the unknown. The premises are always, at the commencement, better known than the conclusion at which we propose to arrive. From this it is evident that we can never reason unless from what is either known or conceded; and, further, that we can never prove any proposition unless we

can find some other proposition better known by which to prove it. If any proposition is to be proved, all other possible propositions must stand to it in one of three relations, either less known, equally known, or better known. To attempt to prove what we know by what we do not know, or to prove what we know by what we do not know as well, is absurd. Inasmuch as proof brings the conclusion to precisely the level of the premises, a process of this kind would diminish instead of increasing the certainty of our conclusion. That an error of this kind cannot be committed, I would not, however, assert. We not unfrequently hear men attempt to prove, what every one at the beginning allows, but which, at the conclusion of the argument, every one is disposed to doubt. Such must always be the result when we attempt to prove self-evident truths. Secondly; to attempt to prove either what we know or what we do not know, by what we only know equally well, is nugatory. We of course know no better at the end than at the beginning of our argument, and all our labor is by necessity thrown away. We could not, by a life's labor in this manner, advance a single step in knowledge. Hence we can never prove any proposition, unless we can find some propositions better known than that which we desire to prove. Hence it follows, that, when we find a proposition so evident that no proposition more evident can be discovered, the truth of such a proposition cannot be established by the reasoning faculty. If it be true, its truth must be determined by some other power of the mind. Hence, all reasoning must commence from truths not made known by the reason, that is, which the intellection perceives to be true previous to all reasoning, and from which all the deductions of reason proceed. Let us consider the nature of some of these elementary beliefs, which lie at the foundation of all reasoning.