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of science, the whole business of human life is closely and strongly connected.
XIII. Evidence arises from reasoning.
One observation, which I made concerning judgment, may be made, with the same propriety, concerning reasoning. It is, itself, a distinct and original source of evidence; and its jurisdiction is exercised also in evidence of every other kind. This suggests a very probable account why reason has been considered by many philosophers as the only source and criterion of evidence: for the powers both of judgment and of reasoning have been frequently blended under the name of
As the conception of judgment should be referred to the faculty of judgment; so the conception of reasoning should be referred to the reasoning faculty, as its source. The ideas of demonstration, of probability, and of all the different modes of reasoning, take their origin from the faculty of reason. Without this faculty, we could not be possessed of those ideas.
The power of reasoning is somewhat allied to the power of judging. Reasoning, as well as judgment, must be true or false : both are accompanied with assent or belief. There is, however, a very material distinction between them. Reasoning is the process, by which we pass from one truth to another as a conclusion from it. In all reasoning, there must be a proposition inferred, and one or more, from which the inference is drawn. The proposition inferred is called the conclusion: the name of premises is given to the proposition or propo. sitions, from which the conclusion is inferred. When a chain of reasoning consists of many links, it is easily distinguished from judgment. But when the conclusion is connected with the premises by a single link, the distinction becomes less obvious; and the process is sometimes called by one name ; sometimes by the other.
In a series of legitimate reasoning, the evidence of every step should be immediately discernible to those who have a distinct comprehension of the premises and the conclusion.
The evidence, which arises from reasoning, is divided into two species-demonstrative and moral. The nature, the difference, and the uses of these two species of evidence, it is of great importance clearly and fully to understand.
Demonstrative evidence has for its subject abstract and necessary truths, or the unchangeable relations of ideas. Moral evidence has for its subject the real but contingent truths and connexions, which take place among things actually existing. Abstract truths have no respect to time or place; they are universally and eternally the same.
If these observations are just and they are agreeable to the sentiments of those who have written most accu. rately on this subject--we may see the impropriety of my Lord Chief Baron Gilbert's remark, when he says, that all demonstration is founded on the view of a man's proper senses.” From hence we may see likewise the inaccuracy of Sir William Blackstone's description of evidence, when he mentions it as demonstrating the very fact in issue. The objects of our senses are objects of moral, but not of demonstrative evidence.
By writers on the civil law, the scientifick distinction, upon this subject, is accurately observed. Truths alone, say they, e which depend on abstract principles, are susceptible of demonstrative evidence: truths, that depend on matters of fact, however complete may be the evi. dence by which they are established, can never become demonstrative.
In a series of demonstrative evidence, the inference, in every step, is necessary; for it is impossible that, from the premises, the conclusion should not flow. In a series of moral evidence, the inference drawn in the several steps is not necessary; nor is it impossible that the premises should be true, while the conclusion drawn from them is false,
In demonstrative evidence, there are no degrees : one demonstration may be more easily comprehended, but it cannot be stronger than another. Every necessary truth leaves no possibility of its being false. In moral evidence, we rise, by an insensible gradation, from possibility to probability, and from probability to the highest degree of moral certainty.
In moral evidence, there not only may be, but there generally is, contrariety of proofs : in demonstrative evidence, no such contrariety can take place. If ong demonstration can be refuted, it must be by another demonstration : but to suppose that two contrary demon.
Encyc. Tit. Jurisprudence, vol. 6. part 2. p. 752. (French)
strations can exist, is to suppose that the same proposition is both true and false : which is manifestly absurd. With regard to moral evidence, there is, for the most part, real evidence on both sides. On both sides, contrary presumptions, contrary testimonies, contrary experiences must be balanced. The probability, on the whole, is, consequently, in the proportion, in which the evidence on one side preponderates over the evidence on the other side.
Demonstrative evidence is simple : in it there is only one coherent series, every part of which depends on what precedes, and suspends what follows. In demonstrative reasoning, therefore, one demonstration is equal to a thousand. To add a second would be a tautology in this kind of evidence. A second, it is true, is sometimes employed; but it is employed as an exercise of ingenuity, not as an additional proof. Moral evidence is generally complicated : it depends not upon any one argument, but upon many independent proofs, which, however, combine their strength, and draw on the same conclusion.
In point of authority, demonstrative evidence is supea riour: moral evidence is superiour in point of importance. By the former, the understanding is enlightened, and many of the elegant and useful arts are improved. By the latter, society is supported; and the usual but indis. pensable affairs of life are regulated. To the acquisitions made by the latter, we owe the knowledge of al. most every thing, which distinguishes the man from the shild.
XIV. Evidence arises from calculations concerning chances. This kind of evidence does not occur very frequently. I take particular notice of it, because it is of much importance in some commercial transactions ; espe=' cially in those relating to ensurances.
Chance furnishes materials for calculation, only when we know the remote cause, which will produce some one event of a given number; but know not the immediate cause, which will determine in favour of any one particular event of that given number, in preference to any other particular event. In calculating chances, it is necessary that a great number of instances be taken into consideration ; that the greatest exactness and impartiali. ty be used in collecting them on the opposite sides; and that there be no peculiarity in any of them, which would render it improper for becoming a part of the basis of a general conclusion.
I have now finished the long, I will not say, the complete enumeration of the different sources and kinds of evidence. Between several of them something will be found to be analogous. But, upon the most careful review, it will, I think, appear, that no one of them can be resolved into any other. Hence the propriety of considering and treating them separately and distinctly. Much advantage will, I believe, be reaped from acquiring and exercising a habit of considering them in this separate and distinct manner. For this
purpose, it will be
proper, when a trial of much variety and importance is perused or heard, to digest, at leisure, those things which are given or which appear in evidence, and refer them to their several sources and kinds. After this has been done, it will be of great use carefully to arrange the dif.