solely and originally derived from the same source, experience.* The utmost in regard to this, that can be affirmed with truth, is, that the evidence of testimony is to be considered as strictly logical, no farther than human veracity in general, or the veracity of witnesses of such a character, and in such circumstances in particular, is supported; or perhaps more properly, hath not been refuted by experience. But that testimony, antecedently to experience, hath a natural influence on belief, is undeniable. In this it resembles memory; for though the defects and misrepresentations of memory are corrected by experience, yet that this faculty hath an innate evidence of its own, we know from this; that if we had not previously given an implicit faith to memory, we had never been able to acquire experience. This will appear from a revisal of its nature, as explained above. Nay, it must be owned, that in what regards single facts, testimony is more adequate evidence than any conclusions from experience. The immediate conclusions from experience are general, and run thus: "This is the ordinary course of nature."—" Such an event may reasonably be expected, when all the attendant circumstances are similar." When we descend to particulars, the conclusion necessarily becomes weaker, being more indirect. For though all the known circumstances be similar, all the actual circumstances may not be similar; nor is it possible in any case to be assured, that all the actual circumstances are known to us. Accordingly, experience is the foundation of philosophy; which consists in a collection of general truths, systematically digested. On the contrary, the direct conclusion from testimony is particular, and runs thus: "This is the fact in the instance specified." Testimony, therefore, is the foundation of history, which is occupied about individuals. Hence we derive our acquaintance with past ages, as from experience we derive all that we can discover of the future. But the former is dignified with the name of knowledge, whereas the latter is regarded as matter of conjecture only. When experience is applied to the discovery of the truth in a particular incident, we call the evidence presumptive; ample testimony is accounted a positive proof of the facts. Nay, the strongest conviction built merely on the former is sometimes overturned by the slightest attack of the latter. Testimony is capable of giving us absolute certainty (Mr. Hume himself being judge,†) even of the most miraculous fact, or of what is contrary to uniform experience. For, perhaps, in no other instance can experience be applied to individual events, with so much certainty, as in what relates to the revolutions of the heavenly bodies. Yet, even this evidence, he admits, may not only be counterbalanced, but destroyed, by testimony.

But to return. Testimony is a serious intimation from another, of any fact or observation, as being what he remembers to have seen, or heard, or experienced. To this, when we have no positive rea

See

* I had occasion to make some reflections on this subject formerly. Dissertation on Miracles, Part I. Sect. 1. There are several ingenious observations on the same subject in Reid's Inquiry, Ch. vi. Sect. 23.

Essay of Miracles, p. 2.

sons of mistrust or doubt, we are, by an original principle of our nature, (analogous to that which compels our faith in memory,) led to give an unlimited assent. As on memory alone is founded the merely personal experience of the individual, so on testimony, in concurrence with memory, is founded the much more extensive experience, which is not originally our own, but derived from others.* By the first, I question not, a man might acquire all the knowledge necessary for mere animal support, in that rudest state of human nature (if ever such a state existed,) which was without speech, and without society; to the last, in conjunction with the other, we are indebted for every thing which distinguishes the man from the brute, for language, arts, and civilization. It hath been observed, that from experience we learn to confine our belief in human testimony within the proper bounds. Hence we are 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, but 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.

* Dissertation on Miracles, Part I. Sec. 2.

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 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 know also, 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 circumstance 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 mathematical 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, 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 conclusion.

PART IV. The superiority of scientific evidence re-examined.

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 show, 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.

It was observed of meinory, that as it instantly succeeds sensation, it is the repository of all the stores from which our experience is collected, and that without an implicit faith in the clear representations of that faculty, we could not advance a step in the acquisition of experimental knowledge. Yet we know that memory is not infallible; nor can we pretend, that in any case there is not a physical possibility of her making a false report. Here, it may be said, is an irremediable imbecility in the very foundation of moral reasoning. But is it less so in demonstrative reasoning? This point deserves a careful examination.

It was remarked concerning the latter, that it is a proof consisting

of an uninterrupted series of axioms. The truth of each is intuitively perceived as we proceed. But this process is of necessity gradual, and these axioms are all brought in succession. It must then be solely by the aid of memory, that they are capable of producing conviction in the mind. Nor by this do I mean to affirm, that we can remember the preceding steps, with their connexions, so as to have them all present to our view at one instant; for then we should, in that instant, perceive the whole intuitively. Our remembrance, on the contrary, amounts to no more than this, that the perception of the truth of the axiom to which we are advanced in the proof, is accompanied with a strong impression on the memory, of the satisfaction that the mind received from the justness and regularity of what preceded. And in this we are under a necessity of acquiescing; for the understanding is no more capable of contemplating and perceiving at once, the truth of all the propositions in the series, than the tongue is capable of uttering them at once. Before we make great progress in geometry, we come to demonstrations, wherein there is a reference to preceding demonstrations; and in these perhaps to others that preceded them. The bare reflection, that as to these we once were satisfied, is accounted by every learner and teacher too, as sufficient. And if it were not so, no advancement at all could be made in this science. Yet here again, the whole evidence is reduced to the testimony of memory. It may be said that, along with the remembrance now mentioned, there is often in the mind, a conscious power of recollecting the several steps, whenever it pleases; but the power of recollecting them severally and successively, and the actual instantaneous recollection of the whole, are widely different. Now what is the consequence of this induction? It is plainly this, that in spite of the pride of mathesis, no demonstration whatever can produce, or reasonably ought to produce, a higher degree of certainty, than that which results from the vivid representations of memory, on which the other is obliged to lean. Such is here the natural subordination, however rational and purely intellectual the former may be accounted, however mysterious and inexplicable the latter. For it is manifest that, without a perfect acquiescence in such representations, the mathematician could not advance a single step beyond his definitions and axioms. Nothing therefore is more certain, however inconceivable it appeared to Dr. Priestley, than what was affirmed by Dr. Oswald, that the possibility of error attends the most complete demonstration.

If from theory we recur to fact, we shall quickly find, that those most deeply versed in this sort of reasoning are conscious of the justness of the remark now made. A geometrician, I shall suppose, discovers a new theorem, which, having made a diagram for the purpose, he attempts to demonstrate, and succeeds in the attempt. The figure he hath constructed is very complex, and the demonstration long. Allow me now to ask, Will he be so perfectly satisfied on the first trial, as not to think it of importance to make a second, perhaps a third, and a fourth? Whence arises this diffidence? Purely from the consciousness of the fallibility of his own faculties. But to what purpose, it may be said, the reiterations of the attempt, since it is im