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INTRODUCTION.

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Robable Evidence is effentially diftinguished from demonftrative by this, that it admits of Degrees; and of all Variety of them, from the highest moral Certainty, to the very lowest Prefumption. We, cannot indeed fay a thing is probably true upon one very flight Prefumption for it; becaufe, as there may be Probabilities on both fides of a Question, there may be fome against it: and though there be not, yet a flight Prefumption does not beget that Degree of Conviction, which is implied in faying a thing is probably true. But that the lightest poffible Prefumption is of the nature of a Probability, appears from hence; that fuch low Prefumption often repeated, will amount even to moral Certainty. Thus a Man's having observed the Ebb and Flow of the Tide to Day, affords fome fort of Presumption, though the lowest imaginable, that it may happen again to Morrow: But the Obfervation of this Event for fo many Days, and Months, and Ages together, as it has been observed by B

Man

Mankind, gives us a full Affurance that it will.

That which chiefly conftitutes Probability is expreffed in the Word Likely, i. e. like fome Truth, or true Event; like it, in itfelf, in its Evidence, in fome more or fewer of its Circumftances. For when we deter- . mine a thing to be probably true, fuppofe that an Event has or will come to pafs, 'tis from the Mind's remarking in it a Likeness to some other Event, which we have obferved has come to pass. And this Obfervation forms, in numberless daily Inftances, a Presumption, Opinion, or full Conviction, that fuch Event has or will come to pafs; according as the Obfervation is, that the like Event has fometimes, most commonly, or always fo far as our Obfervation reaches, come to pass at like Distances of Time, or Place, or upon like Occafions. Hence arifes 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 fuch a Number of days, be its certain Deftruction. So likewife the Rule and Measure of our Hopes and Fears concerning the Succefs of our Pursuits; our Expectations that Others will act fo and fo in fuch Circumftances; and our Judgment

a Verifimile.

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that fuch Actions proceed from fuch Principles; all These rely upon cur having obferved the like to what we hope, fear, expect, judge; I fay upon our having obferved the like, either with respect to Others or Ourfelves. And thus, whereas the Prince who had always lived in a warm Climate, naturally concluded in the way of Analogy, that there was no fuch thing as Water's becoming hard; because he had always obferved it to be fluid and yielding: We on the contrary, from Analogy conclude, that there is no Prefumption at all against This: that 'tis fuppofeable, there may be Frost in England any given Day in January next; probable that there will on fome Day of the Month; and that there is a moral Certainty, i. e. Ground for an Expectation without any Doubt of it, in fome Part or other of the Winter.

Probable Evidence, in its very Nature, af fords but an imperfect kind of Information; and is to be confidered as relative only to Beings of limited Capacities. For Nothing which is the poffible object of Knowledge, whether paft, prefent, or future, can be probable to an infinite Intelligence; fince it cannot but be discerned abfolutely as it is in itself,

b The Story is told by Mr. Locke in the Chapter of Probability.

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certainly true, or certainly falfe. But to Us, Probability is the very Guide of Life.

From these things it follows, that in Queftions of Difficulty, or fuch as are thought so, where more fatisfactory Evidence cannot be had, or is not feen; if the Refult of Examination be, that there appears upon the whole, any the lowest Presumption on One fide, and none on the Other, or a greater Presumption on One fide, 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 abfolute and formal Obligation, in point of Prudence and of Interest, to act upon that Presumption or low Probability, though it be fo low as to leave the Mind in very great Doubt which is the Truth. For furely a Man is as really bound in Prudence, to do what upon the whole appears, according to the best of his Judgment, to be for his Happiness, as what he certainly knows to be fo. Nay further, in Questions of great Confequence, a reafonable Man will think it concerns him to remark lower Probabilities and Prefumptions than thefe; fuch as amount to no more than fhowing One fide of a Queftion to be as fuppofeable and credible as the Other: nay fuch as but amount to much less even than this. For numberless Instances might be mentioned refpecting

respecting the common Pursuits of Life, where a Man would be thought, in a literal Senfe, distracted, who would not act, and with great Application too, not only upon an even Chance, but upon much lefs, and where the Probability or Chance was greatly against his fucceeding.

It is not my Defign to enquire further into the Nature, the Foundation, and Measure of Probability; or whence it proceeds that Likenefs fhould beget that Prefumption, Opinion, and full Conviction, which the human Mind is formed to receive from it, and which it does neceffarily produce in every one; or to guard against the Errors, to which Reasoning from Analogy is liable. This belongs to the Subject of Logick; and is a Part of that Subject which has not yet been thoroughly confidered. Indeed I shall not take upon me to fay, how far the Extent, Compafs, and Force, of analogical Reasoning, can be reduced to general Heads and Rules; and the Whole be formed into a Syftem. 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, affured, that Analogy is of Weight, in various Degrees, towards determining our Judgment, • See Chap. vi. Part II.

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