s a word of nearly the same import with likelihood. It denotes the appearance of truth, or that evidence arising from the preponderation of argument which produces opinion. (See Opinion.) Locke classes all arguments under the heads of demonstrative and probable: Hume with greater accuracy divides them into demonstrations, proofs, and probabilities. Demonstration produces science; proof, belief; and probability, opinion.
Hardly anything is susceptible of strict demonstration besides the mathematical sciences, and a few propositions in metaphysical theology. Physics rest upon principles capable, some of them, of complete proof by experience, and others of nothing more than probability by analogical reasoning. What has uniformly happened, we expect with the fullest confidence to happen again in similar circumstances; what has frequently happened, we likewise expect to happen again; but our expectation is not confident. Uniform experience is proof; frequent experience is probability. The strongest man has always been able to lift the greatest weight; and, therefore, knowing that one man is stronger than another, we expect, with confidence, that the former will lift more than the latter. The best disciplined army has generally proved victorious, when all other circumstances were equal. We therefore expect that an army of veterans will, upon fair ground, defeat an equal number of new levied troops: but as sudden panics have sometimes seized the oldest soldiers, this expectation is accompanied with doubt, and the utmost that we can say of the expected event is, that it is probable; whereas in the competition between the two men, we look upon it as morally certain. (See Metaphysics, part i. chap. vii. sec. 3.) When two or three persons of known veracity attest the same thing as consistent with their knowledge, their testimony amounts to proof, if not contradicted by the testimony of others; if contradicted, it can, at the utmost, amount only to probability. In common language we talk of circumstantial proofs and presumptive proofs; but the expressions are improper, for such evidence amounts to nothing more than probability. Of probability there are indeed various degrees from the confines of certainty down to the confines of impossibility; and a variety of circumstances tending to the same point, though they amount not to what, in strictness of language, should be called proof, afford to the mind a very high degree of evidence, upon which, with the addition of one direct testimony, the laws of many countries take away the life of a man.
Probability of an Event, in the Doctrine of Chance, is greater or less according to the number of chances by which it may happen or fail. (See Expectation.) The probability of life is liable to rules of computation. In the Encyclopedie Methodique, we find a table of the probabilities of the duration of life, constructed from that which is to be found in the seventh volume of the Suppléments à l'Histoire de M. de Buffon; of which the following is an abridgment.
Of 23,994 children born at the same time, there will probably die
| In one year | 7998 | | Remaining 1/2 or 15996 | | | In eight years | 11997 | | Remaining 1/2 or 11997 | | | In thirty-eight years | 15996 | | Remaining 1/2 or 7998 | | | In fifty years | 17994 | | Remaining 1/2 or 5998 | | | In sixty-one years | 19995 | | Remaining 1/2 or 3999 | | | In seventy years | 21595 | | Remaining 1/2 or 2399 | | | In eighty years | 22395 | | Remaining 1/2 or 599 | | | In ninety years | 23914 | | Remaining 1/2 or 80 | | | In a hundred years | 23992 | | Remaining 1/2 or 2. See Bills of Mortality |