No Greek of any calibre, at least in the fifth century, could remain intellectually or spiritually altogether unconditioned by a conscious feeling for, or awareness of, the tragic in human affairs. His poetry and his art, indeed his history, were saturated with the idea of the tragic. Thucydides is certainly no exception, and the most uninformed reader of his History will come away from the work with a keen sense of the immediately perceptible tragic coloration with which it is permeated. Interpreted from any leading, unifying thematic idea the explanation of Thucydides' work must include as central and dominant the tragic deterioration of Athens from the Periclean ideals so well expressed in the Funeral Oration, through the nadir of cynicism and moral decline of the Melian Dialogue, to the utter demoralization expressed through the catastrophe of the Sicilian campaign and its aftermath.
One has merely to examine the obvious and purposefully wrought antitheses throughout the History to determine the dramatic nature of Thucydides' work. The drastic metamorphosis in Athenian character that occurs between Books One and Five, for instance, points up such a tragic contrast. The Athenians of the first assembly at Sparta claim that they more than any others were the saviors of Hellas (1.74.2), fearless and self-sacrificing in the common cause of all allies, that they acted with sagacity of judgement (1.75.1), that the empire had not been acquired by force (1.75.2) but by necessity of circumstances, that they had been more observant of justice than actually required, the overwhelming balance of power being in their favor (1.76.3), that in the courts in Athens suits of allies are judged under the same laws (1.77.1). If we compare these same Athenians with the Athenians of the Melian Dialogue it becomes abundantly clear that a deterioration of character and moral standards has taken place and that Thucydides has linked the moral with the tragic. The earlier Athenians, in spite of their desire for imperial expansion, were at least concerned with a minimum of justice and fair play in their international dealings. The Athenians of the Melian Dialogue do not even make a pretence of upholding the commonly accepted nomoi which had from time immemorial been established among men to protect the weaker. Thucydides' strong editorial statements on the effects of anomia (‘lawlessness’) during and following the plague (2.52-53), and during the stasis on Corcyra (3.81ff.) also make firm the link between the moral and the tragic.