is to fuppofe that the fame propofition is both true and falfe, which is a manifeft contradiction. Confequently, if there fhould ever be the appearance of demonftration on oppofite fides, that on one fide must be fallacious and fophiftical. It is not fo with moral evidence, for unless in a few fingular inftances, there is always real, not apparent evidence on both fides. There are contrary experiences, contrary prefumptions, contrary teftimonies,to balance against one another. In this cafe, the probability, upon the whole, is in the proportion which the evidence on the fide that preponderates bears to its oppofite. We ufually fay, indeed, that the evidence lies on fuch a fide of the queftion, and not on the reverfe; but by this expreffion is only meant the overplus of evidence, on comparing both fides. In like manner, when we affirm of an event, that it is probable, we fay the contrary is only poffible, although, when they are feverally confidered, we do not fcruple to fay, This is more probable than that; or, The probabilities on one fide, outweigh thofe on the other.

THE fourth and laft difference I fhall obferve is, that fcientific evidence is fimple, confifting

of

B. I. of only one coherent feries, every part of which depends on the preceding, and, as it were, fuf pends the following: moral evidence is generally complicated, being in reality a bundle of independent proofs: The longeft demonftration is but one uniform chain, the links whereof, taken feverally, are not to be regarded as fo many arguments, and confequently, 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 fame theorem may be demonftrable in different ways, and by different mediums; but as a fingle demonftration clearly understood, commands the fulleft conviction, every other is fuperfluous. After one demonftrative proof, a man may try a fecond, purely as an exercife of ingenuity, or the better to affure himself that he hath not committed an overfight in the first. Thus it may ferve to warrant the regular procedure of his faculties, but not to make an addition to the former proof, or fupply any deficiency perceived in it. So far is it from anfwering this end, that he is no fooner 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 conclufion 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 fubfift independently of the reft. If you make 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 feveral parts reared above one another, and fo 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 difcriminate them from each other. On a furvey of the whole, it seems indubitable, that if the former is infinitely fuperior 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 almoft entirely confined to quantity, concrete or difcrete. The fphere of Demonstration is narrow, but within her fphere fhe is a defpotic fo

vereign,

vereign, her fway is uncontroulable, Her rival, on the contrary, hath lefs power, but wider empire. Her forces, indeed, are not always irrefiftible; 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 firft, we muft acknowledge, when applied to things, and combined with the difcoveries of the fecond, our refearches 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, fociety muft not only fuffer, but perish. Human nature itfelf could not fubfift. This organ of knowledge, which extends its influence to every precinct of philofophy, and governs in most, serves also to regulate all the ordinary, but indifpenfable concernments of life. To thefe it is admirably adapted, notwithstanding its inferiority in refpect of dignity, accuracy, and perfpicuity. For it is principally to the acquifitions procured by experience, that we' owe the ufe of language, and the knowledge of almoft

1

every thing that makes the foul of a man differ from that of a new-born infant. On the other hand, there is no defpot fo abfolute, as not to be liable to a check on fome fide or other, and that the prerogatives of demonftration are not fo very confiderable, as on a curfory view one is apt to imagine; that this, as well as every other operation of the intellect, muft partake in the weakness incident to all our mental faculties, and infeparable from our nature, I fhall afterwards take an opportunity particularly to evince.

PART II. The nature and origin of Experience.

I SHOULD NOW confider the principal tribes comprehended under the general name of moral evidence; but, that every difficulty may be removed, which might retard our progrefs in the proposed difcuffion, it will be neceffary, in the first place, to explore more accurately those fources in our nature, which give being to experience, and confequently to all thofe attainments, moral and intellectual, that are derived from it. Thefe fources are two, fenfe and memory. The fenfes, both external and internal, are the original inlets of perception. They inform the mind of the facts which, in the prefent

instant,