2. An Athenian, son of Hagnon, and of the demus of Steiria in the tribe Pandionis. According, however, to other statements, he was a native of Cos, and Hagnon only adopted him (Plut. Nic. 2 ; Schol. ad Aristoph. Frogs 541, 968 ; Suid. s. v. Δεξιός). It is doubtful also whether the Hagnon in question was the same as the Athenian founder of Amphipolis; but he must have been at any rate a man of high repute, since we find it mentioned (Xen. Hell. 2.3.30), that Theramenes first acquired notice and respect from the character of his father. In B. C. 411, he became prominent as an oligarchical revolutionist, and a leading member of the new government of the 400 (Thuc. 8.68; Xen. Hell. l.c.). In this, however, he does not appear to have occupied as eminent a station as he had hoped to fill, while at the same time the declaration of Alcibiades and of the army at Samos against the oligarchy made it evident to him that its days were numbered. Acting accordingly with Aristocrates and others, each of whom, like himself, hoped for the foremost place in a restored democracy, he withdrew from the more violent aristocrats and began to cabal against them; professing however to desire, not the overthrow of the existing constitution, but its full establishment, and demanding therefore that the promised assembly of the 5000 should be no longer a name, but a reality. Of this opposition, in fact, Theramenes was the life. He exclaimed against the fortification by the oligarchs of Eetioneia (the mole at the mouth of the Peiraeeus), as part of a design for admitting the enemy into the harbour; for a confirmation of his suspicions he pointed to the fact that the oligarchical ambassadors who had been sent to negotiate peace with Sparta, had returned without having come to any agreement that could be openly avowed; and he insisted that a Peloponnesian fleet, which made its appearance not long after in the Saronic gulf, professedly on its way to help Euboea, was connected with the plot that he was denouncing. He seems also to have instigated the mutiny of the soldiers, who were employed on the works at Eetioneia, and when charged with this by his colleagues in the council, he stoutly denied it, and offered to go down himself and quell the tumult. On his arrival at the scene of disturbance he affected at first to rebuke the mutineers ; but, when they called upon him to declare whether he considered the fortification to be for the public good, he consented to its destruction. In the subsequent deposition of the 400, Theramenes of course took a prominent part, and in particular came forward as the accuser of Antiphon and Archeptolemus, who had been his intimate friends, but whose death he was now the mean and cowardly instrument in procuring (Thuc. 8.89_98; Lys. c. Erat. p. 126; Diod. 13.38). In B. C. 410, Theramenes was sent with 30 ships to prevent the construction of the moles and the bridge, which the Euboeans and Boeotians were building over the Euripus, to connect Euboea with the mainland, and so to render it more defensible against the Athenians. He was unable, however, to interrupt this work; and he then proceeded to cruise among the islands, where he exacted contributions, strengthened the democratic factions, and overthrew the oligarchical government at Paros (Diod. 13.47; comp. Strab. ix. pp. 400, 403, x. p. 407). In the same year he went with a squadron to aid Archelaus, king of Macedonia, in the reduction of Pydna [ARCHELAUS]; but, the siege lasting a long time, he sailed away to Thrace to join the fleet under Thrasybulus, and they then cruised about and levied money until they were called away by a despatch from the Athenian navy at Cardia. The great battle of Cyzicus followed, in which Theramenes commanded one of the three divisions of the Athenian force, the other two being under Alcibiades and Thrasybulus respectively (Xen. Hell. 1.1. §§ 12, &c.; Diod. 13.49_51). Theramenes also shared in the further successes of Alcibiades, and early in B. C. 408, in particular, he took a main part in the siege of Chalcedon, and the reduction of Byzantium. (Xen. Hell. 1.3. §§ 2, &c.; Diod. 13.64, 66, 67.)
At the battle of Arginusae, in B. C. 406, Theramenes held a subordinate command in the right wing of the Athenian fleet, and he was one of those who, after the victory, were commissioned by the generals to repair to the scene of action and save as many as possible of the disabled galleys and their crews. A storm, it is said, rendered the execution of the order impracticable; yet, instead of trusting to this as his ground of defence, Theramenes thought it safer to divert the popular anger from himself to others, and accordingly came prominently forward to accuse the generals of the neglect by which so many lives had been lost; and it appears to have been chiefly through his machinations that those of their number who had returned to Athens, were condemned to death. In his notice of this transaction, Diodorus tells us that the victorious generals endeavoured in the first instance to fix the blame on Theramenes, and thus incurred his enmity; and Theramenes himself, when taxed afterwards by Critias with his base treachery in the matter, is reported by Xenophon to have excused his conduct by a similar allegation. A truly wretched apology at the best ; but even the statement on which it rests is contradicted by Xenophon's narrative, and it seems quite possible (according to bishop Thirlwall's suggestion) that, over and above the cowardly motive of self-preservation, Theramenes may have been, throughout the whole affair, the agent of an oligarchical conspiracy to get rid of some of the most eminent and formidable opponents of that faction. (Xen. Hell. 1.6.35, 7. §§ 4, &100.2.3. §§ 32, 35; Diod.