Part III.

The subdivisions of moral reasoning....III. Testimony.

taught to consider, many attendant circumstances, which serve either to corroborate or to invalidate its evidence. The reputation of the attester, his manner of address, the nature of the fact attested, the occasion of giving the testimony, the possible or probable design in giving it, the disposition of the hearers to whom it was given, and several other circumstances, have all considerable influence in fixing the degree of credibility. But of these I shall have occasion to take notice afterwards. It deserves likewise to be attended to on this subject, that in a number of concurrent testimonies, (in cases wherein there could have been no previous concert) there is a probability distinct from that which may be termed the sum of the probabilities resulting from the testimonies of the witnesses, a probability which would remain even though the witnesses were of such a character as to merit no faith at all. This probability ariseth purely from the concurrence itself. That such a concurrence should spring from chance, is as one to infinite; that is, in other words, morally impossible. If therefore concert be excluded, there remains no other cause but the reality of the fact.

Now to this species of evidence, testimony, we are first immediately indebted for all the branches of philology, such as history, civil, ecclesiastic, and literary; grammar, languages, jurisprudence, and criticism; to which I may add revealed religion, as far as it is to be considered as a subject of historical and critical inquiry, and so discoverable by natural means; and

secondly, to the same source we owe, as was hinted above, a great part of that light which is commonly known under the name of experience, but which is, in fact, not founded on our own personal observations, or the notices originally given by our own senses, buť on the attested experiences and observations of others. So that, as hence we derive entirely our knowledge of the actions and productions of men, especially in other regions, and in former ages; hence also we derive, in a much greater measure than is commonly imagined, our acquaintance with Nature and her works. Logic, rhetoric, ethics, economics, and politics, are properly branches of pneumatology, though very closely connected with the philological studies above enumerated.

IV....Calculations of Chances.

THE last kind of evidence I proposed to consider, was that resulting from calculations of chances. Chance is not commonly understood either in philosophic or in vulgar language to imply the exclusion of a cause, but our ignorance of the cause. It is often employed to denote a bare possibility of an event, when nothing is known either to produce or to hinder it. But in this meaning it can never be made the subject of calculation. It then only affords scope to the calculator, when a cause is known for the production of an effect, and when that effect must necessarily be attended with this or that or the other circumstance; but no cause is known to determine us to regard one particular circumstance, in preference to the rest, as that

Part III. The subdivisions of moral reasoning....IV. Calculation of chances.

which shall accompany the supposed effect. The effect is then considered as necessary, but the circumstance as only casual or contingent. When a die is thrown out of the hand, we know that its gravity will make it fall; we also know, that this, together with its cubical figure, will make it lie so, when intercepted by the table, as to have one side facing upwards. Thus far we proceed on the certain principles of a uniform experience; but there is no principle which can lead me to conclude, that one side rather than another will be turned up. I know that this circum-' stance is not without a cause; but is, on the contrary, as really effected by the previous tossing which it receives in the hand or in the box, as its fall and the manner of its lying are by its gravity and figure. But the various turns or motions given it, in this manner, do inevitably escape my notice; and so are held for nothing. I say, therefore, that the chance is equal for every one of the six sides. Now, if five of these were marked with the same figure, suppose a dagger [+], and only one with an asterisk [*], I should, in that case, say, there were five chances that the die would turn up the dagger, for one that it would turn up the asterisk. For the turning up each of the six sides being equally possible, there are five cases in which the dagger, and only one in which the asterisk, would be uppermost.

THIS differs from experience, inasmuch as I reckon the probability here, not from numbering and comparing the events, after repeated trials, but without

any trial, from balancing the possibilities on both sides.. But, though different from experience, it is so similar, that we cannot wonder that it should produce a similar effect upon the mind. These different positions being considered as equal, if any of five shall produce one effect, and but the sixth another, the mind weighing the different events, resteth in an expectation of that in which the greater number of chances concur; but still accompanied with a degree of hesitancy, which appears proportioned to the number of chances on the opposite side. It is much after the same manner that the mind, on comparing its own experiences, when five instances favour one side, to one that favours the contrary, determines the greater credibility of the former. Hence, in all complicated cases, the very degree of probability may be arithmetically ascertained. That two dice marked in the common way will turn up seven, is thrice as probable as that they will turn up eleven, and six times as probable as that they will turn up twelve*. The degree of probability is here determined demonstratively. It is indeed true, that such mathemetical calculations may be founded on experience, as well as upon chances. Examples of this we have in the computations that have been made of the value of annuities, insurances,

* Call one die A, the other B. The chances for 7 are

Part IV.

The superiority of scientific evidence re-exam ned.

and several other commercial articles. In such cases, a great number of instances is necessary, the greatest exactness in collecting them on each side, and due care that there be no discoverable peculiarity in any of them, which would render them unfit for supporting a general conclusión.

PART IV....The superiority of scientific evidence re-examin d.

AFTER the enumeration made in the first part of this section, of the principal differences between scientific evidence and moral, I signified my intention of resuming the subject afterwards, as far at least as might be necessary to shew that the prerogatives of demonstration are not so considerable, as on a cursory view one is apt to imagine. It will be proper now to execute this intention. I could not attempt it sooner, as the right apprehension of what is to be advanced, will depend on a just conception of those things which have lately been explained. In the comparison referred to, I contrasted the two sorts of evidence, as they are in themselves, without considering the influence which the necessary application of our faculties in using both, has, and ought to have on the effect. The observations then made in that abstracted view of the subject, appear to be well founded. But that view, I acknowledge, doth not comprehend the whole with which we are concerned.

Ir was observed of memory, that as it instantly succeeds sensation, it is the repository of all the stores VOL. I.

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