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is to suppose that the same proposition is both true and false, which is a manifeft contradics tion. Confequently, if there should ever be the appearance of demonftration on oppofite fides, that on one fide must be fallacious and fo. phistical. 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 fay, 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 possible, although, when they are severally considered, we do not fcruple to say, This is more probable than that; or, The probabilities on one side, outweigh thofe on the other.
The fourth and last difference I shall observe is, that scientific eviuence is simple, confifting
of only one coherent series, every part of which depends on the preceding, and, as it were, sufpends the following: moral evidence is generally complicated, being in reality a bundle of independent proofs. The longest demonftration is but one uniform chain, the links whereof, taken severally, are not to be regarded as fo 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 conclufive. It is true, the same theorem may be demonstrable in different ways, and by different mediums; but as a single demonftration clearly understood, commands the fullest conviction, every other is fuperfluous. After one demonstrative proof, a man may try a second, purely as an exercise 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 supply 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 contrary, there is often a combination of many diftinct 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 sublift independently of the reft. If
any breach in it, you defroy 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 characteriftical qualities which discriminate them from each other. On a survey of the whole, it seems indubitable, that if the former is infinitely superior in point of authority, the latter no less excells 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 fo
vereign, her sway is uncontroulable, Her rival, on the contrary, hath less power, but wider empire. Her forces, indeed, are not always irre fiftible; 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 inftitutions of men; in brief, all the beings which fall under the cognizance of the human mind, with all their modifications, operations, and effects. By the first, we must acknowledge, when applied to things, and combined with the discoveries of the second, our researches into nature in a certain line are facilitated, the understanding is enlightened, and many of the arts, both elegant and useful, are improved and perfected. Without the aid of the fecond, society must not only suffer, but perish. Human nature itself could not fubfift. This organ of knowledge, which extends its influence to every precinct of philosophy, and governs in most, serves also to regulate all the ordinary, but indispensable concernments of life. To these it is admirably adapted, notwithstanding its inferiority in respect of dignity, accuracy, and perspicuity. For it is principally to the acquifitions procured by experience, that we'owe the use of language, and the knowledge of almost
every thing that makes the foul of a man differ from that of a new-born infant. On the other hand, there is no despot fo absolute, as not ito be liable to a check on some fide or other, and that the prerogatives of demonstration are not so very confiderable, asi on a cursory view one is apt to imagine ; that this, as well as every other operation of the intellect, must partake in the weakness incident to all our mental faculties, and infeparable from our nature, I shall afterwards take an opportunity particularly to evince.
PART II. The nature and origin of Experience.
I SHOULD now consider the principal tribes comprehended under the general name of moral evidence; but, that every difficulty may be renoved, which might retard our progress in the proposed discussion, it will be néceflary, in the first place;' to explore more accurately those fources in our nature, which give being to 'experience, and consequently to all those attain. nients, moral and intellectual, that are derived from it. These sources are two, fenfe and memory. The fenfes, both external and internal, are the original intets of perception. They inform the mind of the facts which, in the present VOL. I.