« FöregåendeFortsätt »
PROBABLE evidence is essentially distinguished from demonstrative by this, that it admits of degrees ; and of all variety of them, from the highest moral certainty, to the very lowest presumption. We cannot indeed say a thing is probably true upon one very slight presumption for it; because, as there may be probabilities on both sides of a question, there may be some against it: and though there be not, yet a slight presumption does not beget that degree of conviction, which is implied in saying a thing is probably true. But that the slightest possible presumption is of the nature of a probability, appears from hence, that such low presumption, often repeated, will amount even to moral certainty. Thus a man's having observed the ebb and flow of the tide to day, affords some sort of presumption, though the lowest imaginable, that it may happen again to-morrow: But the observation of this event for so many days, and months, and ages together, as it has been observed by mankind, gives us a full assurance that it will.
That which chiefly constitutes probability is expressed in the word likely, i. e like some truth
or true like it, in itself, in its evidence, in some more
or fewer of its circumstances. For when we determine a thing to be probably true, suppose that an event has or will come to pass, 'tis from the mind's remarking in it a likeness to some other event, which we have observed has come to pass. And this observation forms, in numberless daily instances, a presumption, opinion, or full conviction, that such event has or will come to pass ; according as the observation is, that the like event has sometimes, most commonly, or always, so far as our observation reaches, come to pass at like distances of time, or place, or upon like occasions. Hence arises the belief, that a child, if it lives twenty years, will grow up to the stature and strength of a man ; that food will contribute to the preservation of its life, and the want of it for such a number of days be its certain ,destruction. So, likewise, the rule and measure of our hopes and fears concerning the success of our pursuits ; our expectations that others will act so and so in such circumstances; and our judgment that such actions proceed from such principles ;-all these rely upon our having observed the like to what we hope, fear, expect, judge; I say, upon our having observed the like, either with respect to others or ourselves. And thus, whereas the prince *, who had always lived in a warm climate, naturally concluded in the way of analogy, that there was no such thing as water's becoming bard, because he had always observed it to be fluid and yielding ; we, on the contrary, from analogy, conclude, that there is no presumption at all against this ; that 'tis supposable there may be frost in England any given day in January next; probable, that there will on some day of the month ; and that there is a moral certainty, i.e. ground for an expectation, without any doubt of it, in some part or other of the winter.
Probable evidence, in its very nature, affords- but
The story is told by Mr Locke, in the chapter of Probability,
an imperfect kind of information, and is to be con. sidered as relative only to beings of limited capacities. For nothing which is the possible object of knowledge, whether past, present, or future, can be probable to an infinite Intelligence ; since it cannot but be discerned absolutely as it is in itself, certainly true, or certainly false. But, to us, probability is the very guide of life.
From these things it follows, that in questions of difficulty, or such as are thought so, where more satisfactory evidence cannot be had, or is not seen, if the result of examination be, that there appears, upon the whole, any the lowest presumption on one side, and none on the other, or a greater presumption on one side, though in the lowest degree greater, this determines the question, even in matters of speculation ; and, in matters of practice, will lay us under an absolute and formal obligation, in point of prudence and of interest, to act upon that presumption, or low probability, though it be so low as to leave the mind in very great doubt which is the truth. For surely a man is as really bound in prudence to do what upon the whole appears, aceording tə the best of his judgment, to be for his happiness, as what he certainly knows to be so. Nay, further; in questions of great consequence, a reasonable man will think it concerns him to remark lower probabilities and presumptions than these ; such as amount to no more than showing one side of a question to be as supposable and oredible as the other; nay, such as but amount to much less even than this. For numberless instances might be mentioned respecting the common pursuits of life, where a man would be thought, in a literal sense, distracted, who would not act, and with great application too, not only upon an even chanee, but upon much less, and where the probability or chance was greatly against his succeeding *.
* See Chap. vi. Part II.
It is not my design to inquire further into the neture, the foundation, and measure of probability; or whence it proceeds, that likeness should beget that presumption, opinion, and full conviction, which the human mind is formed to receive from it, and which it does necessarily produce in every one ; or to guard against the errors to which reasoning from analogy is liable. This belongs to the subject of logic, and is a part of that subject which has not yet been thoroughly considered. Indeed, I shall not take upon me to say, how far the extent, compass, and force of analogical reasoning, can be reduced to general heads and rules, and the whole be formed into a system. But though so little in this way has been attempted by those who have treated of our intellectual powers, and the exercise of them, this does not hinder but that we may be, as we unquestionably are, assured, that analogy is of weight, in various degrees, towards determining our judgment, and our practice. Nor does it in any wise cease to be of weight in those cases, because persons, either given to dispute, or who require things to be stated with greater exactness than our faculties appear to admit of in practical matters, may find other cases, in which 'tis not easy to say, whether it be, or be not, of any weight ; or instances of seeming analogies, which are really of
It is enough to the present purpose to observe, that this general way of arguing is evidently natural, just, and conclusive. For there is no man can make a question but that the sun will rise to-morrow, and be seen, where it is seen at all, in the figure of a circle, and not in that of a square.
Hence, namely from analogical reasoning, Origen has with singular sagacity observed, that "he who “ believes the Scripture to have proceeded from him
* Xρή μέν τοι γε τον άπαξ παραδεξάμενον τύ κλίσαντος τον κόσμον είναι ταύτας τας γραφάς πεπεισθαι ότι όσα περί της κτίσεως απαντάς τους ζητάει τον περί αυτής λόγον, ταύτα και περί των γραφών, Plilocal. p. 23. Ed. Cant.
la who is the Author of Nature, may well expect to u find the same sort of difficulties in it, as are found " in the constitution of Nature:". And in a like way of reflection, it may be added, that he who denies the Scripture to have been from God, upon account of these difficulties, may, for the very ame reason, deny the world to have been formed by him. On the other hand, if there be an analogy, or likeness, between that system of things and dispensation of Providence, which revelation informs us of, and that system of things and dispensation of Providence, which experience, together with reason, informs us of, i..e. the known course of nature; this is a presumption, that they have both the same author and cause ; at least so far as to answer objections against the former's being from God, drawn from any thing which is analogical or similar to what is in the latter, which is acknowledged to be front him ; for an Author of Na. ture is here supposed
Forming our notions of the constitution and government of the world upon reasoning, without foundation for the principles which we assume, whether from the attributes of God or any thing else, is building a world upon hypothesis, like Descartes. Forma ing our notions upon reasoning from principles which are certain, but applied to cases to which we have no ground to apply them, (like those who explain the structure of the human body, and the nature of diseases and medicines, from mere mathematics, without sufficient data) is an error mueh a-kin to the former : since what is assumed, in order to make the reasoning applicable, is hypothesis. But it must be allowed just, to join abstract reasonings with the observation of facts, and argue from such facts as are known, to others that are like them; from that part of the Divine government over intelligent creatures, which comes under our view, to that larger and more general government over them, which is beyond it; and, from what is present, to collect what is likely, cre. dible, or not incredible, will be hercafter.