Again, “It is true,” says Niebuhr, “that the Trojan war belongs to the region of fable, yet undeniably it has an historical foundation.” But Mr. Grote writes, “If we are asked whether the Trojan war is not a legend ... raised upon a basis of truth, ... our answer must be, that, as the possibility of it cannot be denied, so neither can the reality of it be affirmed.” On the other hand, Mr. Clinton lays down the general rule, “We may acknowledge as real persons, all those whom there is no reason for rejecting. The presumption is in favour of the early tradition, if no argument can be brought to overthrow it.” Thus he lodges the _onus probandi_ with those who impugn the received accounts; but Mr. Grote and Sir George Lewis throw it upon those who defend them. “Historical evidence,” says the latter, “is founded on the testimony of credible witnesses.” And again, “It is perpetually assumed in practice, that historical evidence is different in its nature from other sorts of evidence. This laxity seems to be justified by the doctrine of taking the best evidence which can be obtained. The object of [my] inquiry will be to apply to the early Roman history the same rules of evidence which are applied by common consent to modern history.” Far less severe is the judgment of Colonel Mure: “Where no positive historical proof is affirmable, the balance of historical probability must reduce itself very much to a reasonable indulgence to the weight of national conviction, and a deference to the testimony of the earliest native authorities.” “Reasonable indulgence” to popular belief, “deference” to ancient tradition, are principles of writing history abhorrent to the judicial temper of Sir George Lewis. He considers the words “reasonable indulgence” to be “ambiguous,” and observes that “the very point which cannot be taken for granted, and in which writers differ, is, as to the extent to which contemporary attestation may be presumed without direct and positive proof, ... the extent to which the existence of a popular belief concerning a supposed matter of fact authorizes the inference that it grew out of authentic testimony.” And Mr. Grote observes to the same effect: “The word _tradition_ is an equivocal word, and begs the whole question. It is tacitly understood to imply a tale descriptive of some real matter of fact, taking rise at the time when the fact happened, originally accurate, but corrupted by oral transmission.” And Lewis, who quotes the passage, adds, “This _tacit understanding_ is the key-stone of the whole argument.”