[i] INTRODUCTION. Po Robable Evidence is effentially diftinguished from demonftrative by this, that it admits of Degrees; and of all Variety of them, from the higheft moral Certainty, to the very lowest Prefumption. We cannot indeed fay a thing is probably true upon one very flight Prefumption for it; because, as there may be Probabilities on both fides of a Question, there may be fome againft 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 flighteft. 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 obferved the Ebb and Flow of the Tide to Day, affords fome fort of Presumption, though the loweft 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 Man B 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 determine a thing to be probably true, fuppose that an Event has or will come to pafs, 'tis from the Mind's remarking in it a Likeness to fome other Event, which we have obferved has come to pass. And this Obfervation forms, in numberless daily Inftances, a Prefumption, Opinion, or full Conviction, that fuch Event has or will come to pafs; according as the Obfervation is, that the like Event has fometimes, moft commonly, or always fo far as our Observation 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 Prefervation of its Life, and the Want of it for fuch a Number of Days, be its certain Destruction. So likewife the Rule and Measure of our Hopes and Fears concerning the Success of our Pursuits; our Expectations that Others will act fo and so in such Circumstances; and our Judgment that fuch Actions proceed from fuch Principles; all These rely upon our having obferved the like to what we hope, fear, expect, judge; I fay upon our having obferved the like, either with refpect 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 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 Froft 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, affords 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 past, prefent, or future, can be probable to an infinite Intelligence; fince it cannot but be discerned abfolutely as it is in itself, The Story is told by Mr. Locke in the Chapter of Probability. |