Thucydides, the great historian of the Peloponnesian war, born in the deme Halimus most probably in 471 B.C., was the son of Olorus and Hegesipyle, and was related to Miltiades and Cimon. It is probable that his literary model was Antiphon, and that he was influenced in his views on philosophy by Anaxagoras. Certain it is that, Athenian as he was, of good family, and resident in the most cultivated community in Greece, he must have known Sophocles, Euripides, Aristophanes, Phidias, Protagoras, Gorgias, and possibly Herodotus and Æschylus. He was further possessed, either by inheritance or by acquisition through marriage, of gold-mines in that part of Thrace lying opposite the island of Thasos. We know from himself that he was one of the sufferers from the terrible plague of Athens, and also one of the few who recovered. He held military command, and he had under him an Athenian squadron of seven ships at Thasos, 424 B.C., when he failed to relieve Amphipolis, which fell into the hands of Brasidas. Condemned to death as a traitor, he took refuge in exile and retired to his Thracian estates. His exile enabled him, as he tells us, to associate with the Peloponnesians quite as much as with the Athenians; and he probably spent some time also in Sicily, as we may infer from his minute descriptions of Syracuse and its neighbourhood. According to his own account, he lived in exile twenty years, and probably returned to Athens after the destruction of its walls, in 404. How or when he died is unknown; but he did not live long enough to revise book viii. or to bring his history down to the end of the war.
If Herodotus was 'the father of history,' Thucydides was the first of critical historians, and no better account of his methods can be given than is contained in his own words: 'Of the events of the war I have not ventured to speak from any chance information, nor according to any notion of my own; I have described nothing but what I either saw myself or learned from others, of whom I made the most careful and particular inquiry. The task was a laborious one, because eye-witnesses of the same occurrences gave different accounts of them, as they remembered or were interested in the actions of one side or the other' (i. 22). There is hardly a literary production of which posterity has entertained a more uniformly favourable estimate than the history of Thucydides. This high distinction he owes to his undeviating fidelity and impartiality as a narrator; to the masterly concentration of his work, in which he is content to give in a few simple yet vivid expressions the facts which it must have often taken him weeks or even months to collect, sift, and decide upon; to the sagacity of his political and moral observations, in which he shows the keenest insight into the springs of human action and the mental nature of man; and to the unrivalled descriptive power exemplified in his account of the plague of Athens, and of the Athenian expedition to Sicily. Often, indeed, does the modern student of Greek history share the wish of Grote, that the great writer had been a little more communicative on collateral topics, and that some of his sentences had been expanded into paragraphs, and some of his paragraphs into chapters. But this want cannot have been felt by the contemporaries of Thucydides, while the fate of other ancient historians warns us that had his work, like theirs, been looser in texture, or less severely perfect, it would not have survived, as it has done, the wearing influence of time, or remained, in its own language, the ltema es æi—the 'possession for ever'—it has proved to the world.
It has been reserved for the 19th century to impeach the credibility, depreciate the matter, and to condemn the style of Thucydides. As these indictments, however, usually conclude with the statement that Thucydides remains nevertheless the greatest of historians, they might here be passed over in silence were it not in the first place that they serve to show that Thucydides' fame is proof against the solvents of modern criticism, and next that they help us to a more complete understanding of the qualities which have given to Thucydides' work such a wonderful hold over the intellects and imaginations of all his readers and all his critics. The attacks on Thucydides' credibility have proceeded from Germany (see Müller Sträubung in Jahrb. f. Phil. 131, 289 ff., and his Aristophanes und die historische Kritik, with Lange's reply in the Jahrb. f. Phil. 135, 721-748, and Classen's introduction to Thucydides, v., and Sträubung's rejoinder Thuk. Forschungen), but have met with little acceptance there, and have found only one English-speaking follower, Professor Mahaffy. The most serious outcome of the discussion seems to be that Thucydides' knowledge of the topography of Platææ was defective, and that his account of the siege is consequently in accordance with the situation rather as he conceived it than as it actually was. But, even if we accept this application of the methods of modern criticism, it must not be imagined that those methods have all the same tendency. On the contrary, the actual treaty which Thucydides quotes in v. 47 has been discovered of late years, and confirms the accuracy and truth of the historian in a most unexpected and startling manner. The exact amount of accuracy or inaccuracy in Thucydides' account of the siege of Platææ is matter of opinion; his accuracy in the matter of the treaty is not—it is beyond dispute. But, after all, it is not by tests such as these, welcome as they are, that we can form an adequate opinion on the credibility of Thucydides. As an Athenian comedian remarks, we do not believe a man because he takes an oath—we trust the oath because we believe in the man. And so we believe in Thucydides not because we have external tests to apply (for we have not enough), but because the universal experience of all who read him is a feeling of conviction that his intention was to speak the truth, as far as he could ascertain it. This conviction is ultimately due to the fact that in the man's work we are brought directly into touch with the man, and we judge his character as we judge that of any acquaintance whom we know in the flesh. No man can devote himself for twenty-seven years to composing a work without putting a good deal of himself into the work, or without writing his character down in it—unconsciously but none the less legibly. What then are the qualities of character which impress the reader of Thucydides? In the first place, his impartiality. This is a quality unknown to Latin historians for instance. Tacitus will not admit that the Romans were ever defeated—the result was, at most, indecisive—even though the subsequent movements of the troops, as described by himself, clearly show that the Romans lost. Thucydides, on the other hand, though an Athenian, never extenuates even the mistakes of the Athenians; and though himself banished by them, sets down naught in malice against them. Next, the reader feels that Thucydides strove—and that always—to ascertain facts, and to put down as facts nothing but facts. This conviction is forced on one in many ways, some of which are palpable enough to admit of being clearly indicated. To begin with, there is the fact that, when in search of a subject, Thucydides did not, like all other historians before him, choose a period of ancient history, which, being ancient, must be based on vague hearsay or dim tradition. He preferred contemporary history and events which he himself witnessed in part, while he could obtain the evi- dence of eye-witnesses for the remainder. Nor did he wait until the conclusion of the war before setting about his task; from the very beginning he began collecting his facts. Next, his history is not designed to prove or illustrate any theory. He himself, in the passage quoted above, disclaims all attempt to adapt facts 'to any notion of his own;' and it is evident that beginning to write, as he began, at the commencement of the war, when its course and its issue were yet in the future, he could not have designed to bring its history into conformity with any pre-conceived or a priori theory. Herodotus, writing the history of the past, was in a position to trace the finger of destiny in what had happened, and to explain history by means of final causes. But Thucydides, when he undertook to record the present, thereby deliberately elected to confine himself to efficient causes. This preference for efficient causes and for 'scientific' history, in the best sense of the term, is intimately connected with the 'positive' nature of his history—that is to say, with his perpetual endeavour to record facts and to distinguish them from inferences drawn from facts. A clear consciousness of this difference is involved in one of the most characteristic features of his history—that is, the marked difference between his narrative and the speeches which he introduced into it. The former contains facts and facts only, facts stated with a precision and objectivity which—e.g. in his description of the symptoms of fever in sufferers from the great plague—have been the marvel of all subsequent generations, and the greatest marvel to those who by special professional knowledge are competent to judge. The speeches, on the other hand, are not what the speakers actually said—but of this Thucydides warns the reader at the beginning, showing clearly at once the distinction he drew between facts and inference, and his anxiety that the reader should realise the distinction. In fine, most of the untruth in this world is due not to deliberate perversion, but to the simple fact that so many people are quite unconscious what truth is. When then we find that Thucydides had a conception of historic truth and fact such as 2000 subsequent years have been unable to improve, and that he strove strenuously all his life to live up to that conception and write up to it, we can well understand that even 19th-century criticism acknowledges itself incapable of shaking his credibility.
As for the subject of Thucydides' history, if the Peloponnesian war was not a matter of importance in universal history, it was at least not Thucydides' fault that he was not contemporary with some more important war. But we may beg leave to doubt whether the Peloponnesian war was of inferior interest for the fortunes of mankind. Had it not been for the exhaustion it induced, Greece would not have succumbed to the Macedonian, and consequently Alexander's conquests would never have spread Greek culture over the ancient world. But, apart from this, Thucydides' history is the history of the effects of empire on an imperial state; and, as such, will always be of enthralling interest to citizens of sovereign communities. Finally, Thucydides' style, criticised by Dionysius and condemned by Mure, is in the speeches difficult beyond all possibility of dispute. To throw the blame of this obscurity on the unformed condition of Attic Greek at the time when Thucydides wrote is warrantable indeed, but is no adequate defence. To point, on the other hand, to the tract On the Athenian Polity as proof that Attic prose could be translucent in Thucydides' time is beside the point, for Attic, as is well known, could only be written well by those who lived continuously in Athens, and Thucydides was exiled for many a year. But, in truth, the question whether it is Thucydides or the literary age in which he lived that is to be blamed for his obscurity is a wholly irrelevant question. Obscurity, whatever be its cause, is a crime in a writer. But it is a crime which carries its own punishment, for it diminishes the number of an author's readers. The exact amount of criminality is not to be determined on any abstract principles or by the exercise of any mysterious 'taste': it admits of one simple practical test—viz. has the obscurity of his style (in so far as it exists), as a matter of fact, prevented him from attaining fame? In the case of Thucydides it has had no such effect, as all testify. People will not read a difficult author if there is an easier one out of whom they can get as much. That Thucydides has, in spite of his difficulty, always been read is in itself sufficient testimony that there is no other historian to rank with him.
The best editions are in Latin that of Poppo (11 vols. Leip. 1821-40), in German that of Classen (2d ed., 8 vols. Berlin, 1870-78), and in English—at least for historical illustration—of Arnold (3 vols. Oxford, 1830-35). The best English translation is by Professor Jowett (with a commentary, 2 vols. Clarendon Press, 1881); that by the Rev. Thomas Dale is also good (2 vols. 1848), as is that of the speeches by H. M. Wilkins (2d ed. 1873).