Conjecture.
8. In the same manner, if a man seeth in present that which he hath seen before, he thinks that that which was antecedent to that which he saw before, is also antecedent to that he presently seeth: as for example, he that hath seen the ashes remain after the fire, and now again seeth ashes, concludeth again there hath been fire: and this is called again conjecture of the past, or presumption of the fact.
Signs.
9. When a man hath so often observed like antecedents to be followed by like consequents, that whensoever he seeth the antecedent, he looketh again for the consequent; or when he seeth the consequent, maketh account there hath been the like antecedent; then he calleth both the antecedent and the consequent, signs one of another, as clouds are signs of rain to come, and rain of clouds past.
Prudence.
10. This taking of signs by experience, is that wherein men do ordinarily think, the difference stands between man and man in wisdom, by which they commonly understand a man’s whole ability or power cognitive; but this is an error: for the signs are but conjectural; and according as they have often or seldom failed, so their assurance is more or less; but never full and evident: for though a man have always seen the day and night to follow one another hitherto; yet can he not thence conclude they shall do so, or that they have done so eternally: experience concludeth nothing universally. If the signs hit twenty times for one missing, a man may lay a wager of twenty to one of the event; but may not conclude it for a truth. But by this it is plain, that they shall conjecture best, that have most experience, because they have most signs to conjecture by: which is the reason old men are more prudent, that is, conjecture better, cæteris paribus, than young: for, being old, they remember more; and experience is but remembrance. And men of quick imagination, cæteris paribus, are more prudent than those whose imaginations are slow: for they observe more in less time. Prudence is nothing but conjecture from experience, or taking of signs from experience warily, that is, that the experiments from which he taketh such signs be all remembered; for else the cases are not alike that seem so.
Caveats of concluding from experience.
11. As in conjecture concerning things past and future, it is prudence to conclude from experience, what is like to come to pass, or to have passed already; so it is an error to conclude from it, that it is so or so called; that is to say, we cannot from experience conclude, that any thing is to be called just or unjust, true or false, or any proposition universal whatsoever, except it be from remembrance of the use of names imposed arbitrarily by men: for example, to have heard a sentence given in the like case, the like sentence a thousand times is not enough to conclude that the sentence is just; though most men have no other means to conclude by: but it is necessary, for the drawing of such conclusion, to trace and find out, by many experiences, what men do mean by calling things just and unjust. Further, there is another caveat to be taken in concluding by experience, from the [tenth section] of the second chapter; that is, that we conclude such things to be without, that are within us.