1. The remains of the general literature of the nations of antiquity:—their poetry, and their oratory especially, and their philosophical treatises.
2. Chronological documents or calculations.
3. Facts—geographical and physical, which are unchanged in the lapse of time.
4. Those institutions, usages, or physical peculiarities of nations, which have been subjected to little change.
5. The existing monuments of ancient art—paintings, sculptures, gems, coins, and buildings.
The information derivable from these sources answers two distinct purposes, namely—in the first place, that of contributing to the amount of our knowledge of the state of civilization among ancient nations; and then that of furnishing the means of corroborating or of correcting the assertions of historians on particular points. It is obvious that to go through the particulars that are comprehended under the general heads above-named, or to do so with any degree of precision, would greatly exceed the limits of this book; indeed, the object aimed at in it will be sufficiently attained by merely pointing out, in a few instances, what is the nature, and what is the value of this sort of corroborative evidence.
1. Corroboratory evidence, derived from books—coming as it does through similar, if not the very same channels with those through which we receive the works of historians, and being of the same external form—is likely to produce less impression on the mind than its real validity ought to command. And yet, when it comes to be examined in detail, nothing can be more conclusive than the proof which thus arises from coincidences of names and allusions, such as are found scattered through the works of dramatists, orators, poets, and philosophers, with the more formal statements of contemporary historians. If, for example, the Greek dramatic writings—those of Æschylus, Sophocles, Euripides, Aristophanes, and the Orations of Demosthenes, are collated with the narrations of Thucydides, Xenophon, Diodorus, and Plutarch;—or if the Epistles and the Orations of Cicero, and the Satires of Horace, and of Juvenal, are compared with the historical works of Livy, of Sallust, of Tacitus, and of Dion Cassius, so many points of agreement present themselves, as must convince every one that these historical assertions, and these allusions, must have had a common origin in actual facts.
Yet it is not merely by presenting special coincidences, on particular points, that the remains of ancient literature confirm the evidence of historians; but it is also by furnishing such pictures of the people among whom they were current, as to all points of their political, religious, and social condition, as consist with the representations of historians. To exhibit the full force of this sort of evidence, let it be imagined that the names of men, and of cities, and countries, having been withdrawn from the works of the classical poets, orators, and philosophers, it were attempted to associate, as countrymen and contemporaries, Herodotus, Thucydides and Xenophon, with Cicero, Horace and Seneca; or Tacitus, Cæsar and Suetonius, with Isocrates, Plato and Æschylus: every page in the one class of writers, would present some incongruity with the accounts given of the people by the others. On the contrary, in perusing the contemporary writers of the same nation, whatever may be the diversities of their style or subject, we feel that they were all surrounded by the same objects, and that they were subjected to the same influences.
2. Those corroborative evidences that are derived from chronological inscriptions, or from astronomical calculations, have served in some notable instances to confirm, or to correct, the testimony of ancient writers, in a very conclusive manner. It should be remembered that ancient historians, being destitute for the most part of sufficiently precise chronological information, and being themselves also less observant of dates than the modern style of historical composition demands, leave the subject open to many difficulties; and to these difficulties is added that uncertainty which belongs peculiarly, as we have before remarked, to whatever relates to numbers, in the text of ancient authors. It must not however be supposed that ancient chronology is altogether unfixed; for though it may be impossible now to determine the precise time of many events, the results of different lines of calculation are seldom so widely discordant as to be of much importance in the general outline of history.
3. Those inequalities of the earth’s surface which have undergone no great change within the historic period, and also the course of rivers, and the peculiarities of climate, and the vegetable and animal productions of each country, though they are not absolutely immutable, have not, even in the lapse of many ages, undergone any such changes as to perplex us in fixing the identity of ancient and modern names. There are now open to our observation, the same scenes, and the same physical appearances which were described, or alluded to, by historians, twenty centuries ago; and finding, as we do, their accounts of these permanent objects to accord with present and well-known facts, we accept such coincidences as a pledge of the general accuracy and authenticity of the writings in question: for if an historian is proved to have been careful to obtain correct information on points that were indirectly connected with his subject, it is but just to believe that he was at least equally exact in regard to events, and to what belongs more immediately to his narrative.