III. Very early in life Themistokles took a vigorous part in public affairs, possessed by vehement ambition. Determined from the very outset that he would become the leading man in the state, he eagerly entered into all the schemes for displacing those who where then at the head of affairs, especially attacking Aristeides, the son of Lysimachus, whose policy he opposed on every occasion. Yet his enmity with this man seems to have had a very boyish commencement; for they both entertained a passion for the beautiful Stesilaus, who, we are told by Ariston the philosopher, was descended from a family residing in the island of Keos. After this difference they espoused different parties in the state, and their different temper and habits widened the breach between them. Aristeides was of a mild and honourable nature, and as a statesman cared nothing for popularity or personal glory, but did what he thought right with great caution and strict rectitude. He was thus often brought into collision with Themistokles, who was trying to engage the people in many new schemes, and to introduce startling reforms, by which he would himself have gained credit, and which Aristeides steadily opposed.
He is said to have been so recklessly ambitious and so frenziedly eager to take part in great events, that though he was very young at the time of the battle of Marathon, when the country rang with the praises of the generalship of Miltiades, he was often to be seen buried in thought, passing sleepless nights and refusing invitations to wine-parties, and that he answered those who asked him the cause of his change of habits, that the trophies of Miltiades would not let him sleep. Other men thought that the victory of Marathon had put an end to the war, but Themistokles saw that it was but the prelude to a greater contest, in which he prepared himself to stand forth as the champion of Greece, and, foreseeing long before what was to come, endeavoured to make the city of Athens ready to meet it.