It is generally a theory--a theory, perhaps unconsciously formed, but still a theory. Certain phenomena, of which there is no historical explanation, excite the notice of some one less incurious than his fellows, and he attempts to account for them. On the two opposite coasts of a sea--for instance--two populations with the same manners and language, are observed to reside. A migration will account for this; and, consequently, a migration is assumed. The view, being reasonable, is generally adopted; and the fact of a migration having absolutely taken place becomes the current belief. The men who speak of this in the fourth or fifth generation, speak of it as an actual occurrence. So, perhaps, it is. But it is no tradition notwithstanding; since the record cannot be traced up to the event. All that posterity has had handed-down from its ancestors, is an _inference_; which, even if it be as good as the historical account of an absolute event (as it sometimes is), is anything but a tradition in the strict sense of the term. Of course, the existence of the inference itself can be reduced to a fact, and, as such, produce a tradition. But this is not the tradition which is wanted--not the tradition which gives the fact in question. These _ex post facto_ traditions may be of any amount of value, or of any degree of worthlessness. They may be inferences of such accuracy and justice as to command the respect of the most critical; or they may involve impossibilities. The extremes are the best; the former for their intrinsic value, the latter from their unlikelihood to mislead. The most dangerous are the intermediate. Possibly, plausible, or, at any rate, without any outward and visible marks of condemnation-- "They lie like truth, and yet most truly lie." What proportion do these _ex post facto_ traditions bear to the true ones? This is difficult to say. A nickname, a genealogy, a tune may well be transmitted by tradition. So may charms, formulæ, proverbs, and poems; yet when we come to proverbs and poems we are on the domain of unwritten literature, a domain which can scarcely be identified with that of tradition. A local legend, when it is not too suspiciously adapted to the features of the place to which it applies, may also be admitted as traditional. These and but little beyond. Men rarely think about transmitting narratives until it is too late for an authentic account.