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DEMONSTRATIVE AND MORAL REASONING.
premises. Even in the higher branches of mathematics, however subtle the reasoning employed, and however closely it may border on that limit where science merges into speculation, it never admits an uncertainty, or advances a proposition which is not the inevitable consequence of some foregone proof. Moral truths might also be demonstrated if we could agree on the meaning of words; but a slight difference with regard to this meaning so alters the relations of the ideas expressed, that the conclusions drawn from them cease to be valid. In demonstrating a mathematical theorem, we speak of a triangle, or a right angle, with the perfect certainty that those terms convey the same idea to every one who has ever read the definition of a triangle, or a right angle. But if we reason on moral subjects, the same words may convey different ideas to different persons. and consequently the argument, which is conclusive to some, may be quite inconclusive to others. Suppose, for instance, an argument on the necessity of education to improve the moral condition of the people, education being understood by those who uphold the argument, to mean the training and development of all the faculties, and the formation of good moral and mental habits. To those who agree in this definition, the argument has all the force of a demonstration, but to those who define education as the mere teaching to readand write, the proof will not only fail to carry conviction, but will perhaps remain in their minds below probability.
The difficulty, amounting almost to impossibility, of defining terms of this complex nature with the perfect precision attainable in mathematics, must always be a serious drawback to the progress of moral and metaphysical science. The only remedies are increased caution on the part of writers on such subjects to define their terms as precisely as possible, and to use them only in the sense thus defined; and increased care on the part of the reader, to attend to the definitions, and bear them clearly in mind whilst examining his author's argument. A reader who neglects these precautions, will be liable to substitute his own meaning of the terms for that of the author, and thereby to misunderstand the whole argument; or if the terms convey to him only vague and indefinite notions, he may read on for ever without perceiving the truth intended to be proved, or knowing why he does not perceive it. There are two reasons for objecting to a proof; either the reasoning is incorrect, or the premises are false. But it is clear that whoever has not attended to the definition of the terms in which these premises are stated, can neither judge whether the premises are false, or the reasoning from them incorrect. Such a person will on that subject never arrive at the truth.
The small amount of demonstrative truth that we possess, gives its great value to the evidence by which the probability of truth may be established. Probability is the ground on which we are forced to rest most of our opinions and decisions. If we were to act only on what can be demonstrated to be true, or form no opinions but on grounds demonstratively proved, we should fall into almost universal scepticism, and be reduced to remain mere idle spectators in the world. Strictly speaking, indeed, demonstration alone is proof, but our minds are so constituted, that on certain questions, which do not allow of the strict form of proof, we admit moral certainty with as little hesitation as demonstrative evidence. The conclusion cannot be proved, but it appeals to certain principles of belief, which are stronger than any deduction of the understanding; and hence it is, that the all-important questions of religion and morals stand on a basis as indestructible as that of pure science, though not admitting of being established by the same process. In all questions relating to the business of life, even the most important, we act upon probability. It is as Dr. Butler has said, "The rule of life." No man thinks of waiting to decide upon any practical question till he can get demonstrative evidence, but having carefully collected and weighed such evidence as he can procure, he forms a judgment, and acts upon it, without regard to the degree of doubt which must still rest on every decision formed on probable evidence. This is the only wise and prudent course. Such a degree of doubt we must bear with on all practical matters, and there is not only unfairness and prejudice, but a great error of reasoning, in refusing to adhere, when considering moral and religious questions, to the same rule by which we are guided in all others, whatever their importance, which do not admit of positive demonstration.
It is of great importance that we should accustom ourselves to discriminate justly between different subjects with regard to the different kinds of proof which they admit of. "The rigour and curiosity," says Lord Bacon, "in requiring the severe proofs in some things, and chiefly the facility in contenting ourselves with the more remiss proof in others, hath been among the greatest causes of detriment and hindrance to knowledge." This error is owing to a radical defect in reasoning, which conceals itself under a specious garb of uniformity and rigorous exactness. When the study of certain subjects shows them to differ in their very nature (as mathematics, for instance, and moral questions, the one relating to abstract truth, the other to points of practical experience), reasoning fairly conducted on such grounds, leads to the conclusion that they cannot admit of the same degree or manner of proof; that were positive demonstration attainable in the one, or
probable evidence admissible in the other, the very order and constitution of the objects themselves must be changed; and, therefore, that to require this uniformity, is as much an error of reasoning as always to expect a positive conclusion, whether the premises given be positive or hypothetical. Nothing, however, is more common than to see persons who have confined their inquiries very much to one province, fall into this error of judgment, however acute their reasoning powers may be in other respects. We hear metaphysicians despising the positive nature of physical science, and mathematicians scorning the uncertainties of moral and political questions, demanding strict proof as the condition of their assent to propositions which in their very nature do not admit of such a proof, or turning away with pain from subjects which excite our strongest sympathies, and appeal to our highest interests, because the knowledge of absolute truth is not therein vouchsafed to us.
In training ourselves to the severe exercise of reason, this snare, which lurks in some of the studies best fitted for the purpose, must be carefully guarded against. In first trying to call forth the power of reasoning, it is often hard to make the mind, accustomed to indolent acquiescence, feel any want of proof, and we are forced to continue so long insisting on its necessity, that we are apt to pass the bounds where positive proof can be given. Unreasoning minds never feel doubt; but when reason is awakened, and attention turned to the examination of our own principles and opinions, doubts and difficulties start up in multitudes. Nor is it till considerable time and labour have been spent in reflecting upon such subjects, in comparing them with others, and apprehending the difference of their very nature from that of positive science, that the mind loses the unsettled, confused feeling, which results from the first disturbance of its unreasoning, undoubting confidence. The greatest care is then necessary to preserve the right balance, to maintain the free and earnest exercise of reason in the search after truth, together with the recollection that our utmost efforts in that search must often fail, and that we must neither attempt to supply the deficiency by ungrounded imaginations, nor reject such portions as we can acquire, because the whole to which they belong is not revealed to us.
The amount of absolute knowledge is scanty indeed! Truth may be the glorious inheritance of a higher stage of existence, when we shall have passed from this "twilight state" into perfect day; but here we have only glimmerings, enough to inspire our souls with love for its immortal beauty, not enough to satisfy our earnest cravings. But in this very privation there is also a consolation, for by it we are perpetually reminded that the end of
our labours is not here; we are preserved from the pride which ignorance and folly alone can feel on earth, and the conviction is more and more deeply wrought into our minds that the present is but a low beginning of existence, where the soul is pining as in a house of bondage. Then, when weary with the so often fruitless search after truth, forced again and again to rest content with doubt, we would give worlds to rend aside the veil of darkness which surrounds us, with what force does the promise that ". we shall know even as we are known" come home to the heart, giving sanction to each ardent aspiration, answering each trembling hope. There are, indeed, few proofs of our immortal destiny so strong as the yearnings after truth which in this life can never be satisfied!
The difficulty of attaining to a knowledge of absolute truth does not imply that we are to be satisfied with vague and uncertain conclusions. There are as many degrees of probability as there are steps between a wholly unsupported assertion and that amount of proof which produces moral certainty; that is, the highest degree of certainty that can be obtained on any subject beyond the limits of demonstration. We attain moral certainty when the relations we are investigating are so in accordance with other known relations, when they so agree with previous knowledge, or with the results of our own consciousness, that, although beyond the possibility of demonstration, nothing but direct proof of the contrary could shake our belief in them. This is the highest certainty reason can attain on many questions of the deepest importance, and it is sufficient for the mind to rest upon, as the strong and immoveable basis of action and principle; yet, as the force of the proof depends upon the previous knowledge and modes of thought and feeling of the mind to which it is addressed, there must inevitably be wide differences in the conclusions arrived at, on almost every subject but those where the common feelings of human nature ensure a certain uniformity of sentiment. To insist on greater unanimity than this, is to insist upon an impossibility. The conclusions founded on moral certainty assume the name of principles. In speculative questions they are such as, being supported by the highest degree of evidence, are assumed as the foundations of further reasoning. In morals they are such as conscience has sanctioned no less than reason, and which become, therefore, rules of action.
Conclusions which rest on a lower degree of evidence, and are open to greater uncertainty than principles, are simply opinions. They are more or less sound in proportion to the validity of the evidence on which they rest, and to the care with which they have been reasoned out from that evidence; and to maintain them any further than such evidence warrants, is to sacrifice truth to
vanity or prejudice. As the formation of opinion is in some respects the most essential exercise of reason, so is it in some measure the most difficult, because impeded by obstacles which do not lie in the path of scientific investigation. We have spoken of those difficulties with regard to the definition of terms which makes demonstration impossible in a certain class of subjects; but when to this difficulty is added that which results from the passions of mankind being enlisted on one side or the other of all questions on which it is most important to form sound opinions, it will be seen how indispensable it is that we should weigh and examine all these difficulties, so as to prevent their impeding the free and assured use of reason in the pursuit of truth.
SECT. III.-MORAL OBSTACLES TO PERCEPTION OF TRUTH.
Ir is to the moral condition of our own minds that we may trace the obstacles which principally impede our perception and admission of truth. These are what Lord Bacon terms "the idols of the den." "Every man," says he, "has his own peculiar den or cavern which breaks and corrupts the light of nature, either on account of his constitution and disposition of mind, his education and the society he keeps, his course of reading and the authorities he most respects, his peculiar impressions, as they may be made on a mind that is preoccupied and prepossessed, or is in a calm unbiassed frame."
The fact that these "idols" of passion, prejudice and association, derive their strong hold over the mind from the influence of the feelings over the judgment, affords a striking illustration of the connexion between our moral and intellectual nature, and the importance of moral discipline to the free and successful use of the intellect. The difficulty of arriving at truth arises much more frequently from the infirmity of our moral nature, than from that of our reason. The latter, if properly cultivated and unbiassed by feeling, will seldom err in cases where the terms of the proposition are clearly understood, and competent knowledge is possessed of the facts of the case. But if our feelings be enlisted on one side or the other, they prevent reason from coming fairly into operation, and perceiving a truth which militates against the cherished error. Whenever a truth has been long and obstinately opposed, the opposition has arisen, not from intellectual difficulties, but from passion. The question has been judged, not on its own merits, but on its incompatibility with opinions bound up with the interests and passions of the judges.
Our nature is so constituted that our affections, which are the