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Fo -i. Part I. Scientific and moral, with the principal distinctions between them. sites. The proper province of rhetoric is the second, or moral evidence; for to the second belong all decisions concerning fact, and things without us.
BUT that the nature of moral evidence may be better understood, it will not be amiss to remark a few of the most eminent differences between this and the demonstrative,
THE first difference that occurs is in their subjects. The subject of the one is, as hath been observed, abstract independent truth, or the unchangeable and necessary relations of ideas; that of the other, the real, but often changeable and contingent connexions that subsist among things actually existing. Abstract truths, as the properties of quantity, have no respect to time or to place, no dependence on the volition of any being, or on any cause whatever, but are eternally and immutably the same. The very reverse of all this generally obtains with regard to fact. In consequence of what has been now advanced, assertions opposite to truths of the former kind, are not only false, but absurd. They are not only not true, but it is impossible they should be true, whilst the meanings of the words, (and consequently the ideas compared) remain the same. This doth not hold commonly in any other kind of evidence. Take, for instance, of the first kind, the following affirmation: “The cube of two is the half of sixteen.” “The “square of the hypotenuse is equal to the sum of the “squares of the sides.” “.. If equal things be taken
“from equal things, the remainders will be equal.” Contrary propositions, as, “ The cube of two is more “than the half of sixteen.” “ The square of the hy“potenuse is less than the sum of the squares of the “sides.” “if equal things be taken from equal things, “the remainders will be unequal,” are chargeable, not only with falsity, but with absurdity, being inconceivable and contradictory. Whereas, to these truths which we acquire by moral evidence, “Caesar “overcame Pompey.” “The sun will rise to-morrow.” “All men will die,” the opposite assertions, though untrue, are easily conceivable without changing, in the least, the import of the words, and therefore do not imply a contradiction.
THE second difference I shall remark is, that moral evidence admits degrees, demonstration doth not. This is a plain consequence of the preceding difference. Essential or necessary truth, the sole object of the latter, is incompatible with degree. And though actual truth, or matter of fact, be the ultimate aim or the former, likelihood alone, which is susceptible of degree, is usually the utmost attainment. Whatever is exhibited as demonstration, is either mere ilIusion, and so no evidence at all, or absolutely perfect. There is no medium. In moral reasoning we ascend from possibility, by an insensible gradation, to probability; and thence, in the same manner, to the summit of moral certainty. On this summit, or any of the steps leading to it, the conclusion of the argument may rest, Hence the result of that is, by way of
Part I. Scientific and moral, with the principal distinctions between them.
eminence, denominated science; and the evidence itself is termed scientific; the result of this is frequently (not always) entitled to no higher denomination than opinion. Now, in the mathematical sciences, no mention is ever made of opinions.
THE third difference is, that in the one there never can be any contrariety of proofs; in the other, there not only may be, but almost always is. If one demonstration were ever capable of being refuted, it could be solely by another demonstration, this being the only sort of evidence adapted to the subject, and the only sort by which the former could be matched, But, to suppose that contrarities are demonstrable, is to suppose that the same proposition is both true and false, which is a manifest contradiction. Consequently, if there should ever be the appearance of demonstration on opposite sides, that on one side must be fallacious and Sophistical. It is not so with moral evidence, for unless in a few singular instances, there is always real, not apparent evidence on both sides. There are contrary experiences, contrary presumptions, contrary testimonies, to balance against one another, In this case, the probability, upon the whole, is in the proportion which the evidence on the side that preponderates bears to its opposite. We usually say, indeed, that the evidence lies on such a side of the question, and not on the reverse; but by this expression is only meant the overplus of evidence, on comparing both sides. In like manner, when we affirm of an event, that it is probable, we say the contrary is only
Sect. II. Of deductive evidence.
possible, although, when they are severally considered, we do not scruple to say, This is more probable than that; or, The probabilities on one side, outweigh those on the other. -
THE fourth and last difference I shall observe is, that scientific evidence is simple, consisting of only one coherent series, every part of which depends on the preceding, and, as it were, suspends the following: moral evidence is generally complicated, being in reality a bundle of independent proofs. The longest demonstration is but one uniform chain, the links whereof, taken severally, are not to be regarded as so many arguments, and consequently, when thus taken, they conclude nothing; but, taken together, and in their proper order, they form one argument, which is perfectly conclusive. It is true, the same theorem may be demonstrable in different ways, and by different mediums; but as a single demonstration clearly understood, commands the fullest conviction, every other is superfluous. After one demonstrative proof, a man may try a second, purely as an excercise of ingenuity, or the better to assure himself that he hath not committed an oversight in the first. Thus it may serve to warrant the regular procedure of his faculties, but not to make an addition to the former proof, or suply any deficiency perceived in it. So far is it from answering this end, that he is no sooner sensible of a defect in an attempt of this nature, than the whole is rejected as good for nothing, and carrying with it no degree of evidence whatever. In moral reasoning, on the con
Part I.....Scientific and moral, with the principal distinctions between them.
trary, there is often a combination of many distinct
topics of argument, noway dependent on one another. Each hath a certain portion of evidence belonging to itself, each bestows on the conclusion a particular degree of likelihood, of all which accumulated, the credibility of the fact is compounded. The former may be compared to an arch, no part of which can subsist independently of the rest. If you make any breach in it, you destroy the whole. The latter may be compared to a tower, the height whereof is but the aggregate of the heights of the several parts reared above one another, and so may be gradually diminished, as it was gradually raised.
So much for the respective natures of scientific and of moral evidence, and those characteristical qualities which discriminate them from each other. On a survey or the whole, it seems indubitable, that if the former is infinitely superior in point of authority, the latter no less excels in point of importance. Abstract truth, as far as it is the object of our faculties, is almost entirely confined to quantity, concrete or discrete. The sphere of Demonstration is narrow, but within her sphere she is a despotic sovereign, her sway, is uncontroulable, Her rival, on the contrary, hath less power, but wider empire. Her forces, in deed, are not always irresistable; but the whole world is comprised in her dominions. Reality or fact comprehends the laws and the works of nature, as well as the arts and the institutions of men; in brief, all the beings which fall under the cognizance of the human