14 Sept 1803

Evidence

Instructions

Considerations in [...?]

Improbability

When a fact is considered as being to such a degree improbable, as not to be capable of being proved by any quantity even of the best evidence it is commonly termed impossible. Improbability or impossibility it or their physical, that is natural or moral fact is /may be/ said to be physically improbable, when it is considered as being inconsistent with the established and known order of things with any of those rules and propositions which have been deduced from the universal /general/ observation of mankind, and are termed laws of nature, such as for instance that which asserts as a known matter of fact, the weight or gravity of all the bodies that we see in, upon or near to this our earth: that property whereby if a man jumps up from the surface of the earth, he feels himself drawn down again.

A fact is said to be morally improbable, when it is considered as being inconsistent with the known course of human conduct. This species /sort/ of improbability is confined to such facts as take place /have their place/ in the human mind: such as the harbouring /entertaining/ of such and such perceptions, conceptions, intentions, wishes: the being actuated by such and such motives, under the existing circumstances of the case.

The degree of distrust produced in the breast of a Judge by the improbability of the alledged fact, when that improbability is of the physical kind, as above, will depend upon the confidence he has in his own knowledge respecting the powers and order of nature so far as the particular fact in question is concerned. if he have any doubt, he will do well to have recourse to scientific evidence: to call in the opinion of such persons as by their professional situation or reputation are pointed out to him as being particularly well informed in relation to matters of that sort. Thus suppose upon the testimony of two witnesses a demand made upon a man for money in satisfaction for damage done to a gardens ground by the fall of the first inhabited air-balloon that ever was and by reflection on the weight of bodies supposed the Judge to have been inclined to disbelieve the testimony, on the ground of the apparent improbability of the fact. In such case he would have done well to call in the opinion of some lecturer or lecturer on natural philosophy. And accordingly supposing him so to have done, he would have learnt from them that there was really no inconsistency between what he had always observed and heard concerning the heaviness of bodies in general, and what the witnesses had been [...?] concerning the extraordinary lightness of the particular body so raised.