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with the past experience. Reasoning may be employed in bringing the inftances into view; but when that is done, it is no, longer neceffary. And if you were to argue with a man, in order to convince him that a certain future event is not fo improbable as he feems to think, you would only make him take notice of fome favourable inftance which he had overlooked, or endeavour to render him fufpicious of the reality of fome of the unfavourable instances; leaving it to himself to estimate the degree of probability. If he continue refractory, notwithstanding that his view of the fubject is the fame with yours, he can be reafoned with in no other way, than by your appealing to the common fenfe of mankind.
Of Analogical Reafoning.
REafoning 'from analogy, when traced
up to its fource, will be found in like manner to terminate in a certain instinctive propensity, implanted in us by our
Maker, which leads us to expect, that fimilar caufes in fimilar circumstances, do probably produce, or will probably produce, fimilar effects. The probabi lity which this kind of evidence is fitted to illuftrate, does, like the former, admit of a vast variety of degrees, from abfolute doubting up to moral certainty. When the ancient philofopher who was fhipwrecked in a strange country, difcovered certain geometrical figures drawn upon the fand by the fea-fhore, he was very naturally led to believe, with a degree of affurance not inferior to moral certainty, that the country was inhabited by men, fome of whom were men of ftudy and fcience, like himfelf. Had thefe figures been lefs regular, and liker the appearance of chance-work, the prefumption from analogy, of the country being inhabited, would have been weaker; and had they been of fuch a nature as left it altogether dubious, whether they were the work of accident or of defign, the evidence would have been too ambiguous to ferve as a foundation for any opinion,
In reafoning from analogy, we argue from a fact or thing experienced to fome
thing fimilar not experienced; and from our view of the former arifeth an opinion with regard to the latter; which opinion will be found to imply a greater or less degree of affurance, according as the instance from which we argue is more or lefs fimifar to the inftance to which we argue. Why the degree of our affurance is determined by the degree of likeness, we cannot tell; but we know by experience, that this is the cafe and we alfo know by experience, that our affurance, fuch as it is, arifeth immediately in the mind, whenever we fix our attention on the circumftances in which the probable event is expected, fo as to trace their refemblance to thofe circumftances in which we have known a fimilar event to take place. A child who has been burnt with a red-hot coal, is careful to avoid touching the flame of a candle; for as the vifible qualities of the latter are like to thofe of the former, he expects, with a very high degree of affurance, that the effects produced by the candle, operating on his fingers, will be fimilar to thofe produced by the burning coal. And it deferves to be remarked, that the judgement which a child forms
on thefe occafions may arife, and often doth arife, previous to education and reafoning, and while experience is very limit ed. Knowing that a lighted candle is a dangerous object, he will be fhy of touching a glow-worm, or a piece of wet fish fhining in the dark, becaufe of their refemblance to the flame of a candle: but as this resemblance is but imperfect, his judgement, with regard to the confe→ quences of touching thefe objects, will probably be more inclined to doubt, than in the former cafe, where the instances were more fimilar. Those who are acquainted with aftronomy, think it extremely probable, that the planets are inhabited by living creatures, on account of their being in all other refpects fo like to our earth. A man who thinks them not much bigger than they appear to the eye, never dreams of fuch a notion; for to him, they seem in every refpect unlike to our earth: and there is no other way of bringing him over to the aftronomer's opinion, than by explaining to him those particulars in which the planets and our earth refemble one another. As foon as he comprehends these particulars, and this refem
blance, his mind of its own accord admits the probability of the new opinion, without being led to it by any medium of proof, connecting the facts he hath experienced with other fimilar and probable facts lying beyond the reach of his experience. Such a proof indeed could not be given. If he were not convinced of the probability by the bare view of the facts, you would impute his perfeverance in his old opinion, either to obftinacy, or to want of common fenfe; two mental diforders for which logic provides no remedy.
SE CT. VIII.
Of Faith in Teftimony.
THere are many men in the world, whofe declaration concerning any fact which they have seen, and of which they are competent judges, would engage my belief as effectually as the evidence of my own fenfes. A metaphyfician may tell me, that this implicit confidence in teftiis unworthy of a philofopher and a logician,