Ariston, king of Sparta, had been married to two wives, but neither of them had borne him any children; as however he still thought it was possible he might have offspring, he resolved to wed a third; and this was how the wedding was brought about. He had a certain friend, a Spartan, with whom he was more intimate than with any other citizen. This friend was married to a wife whose beauty far surpassed that of all the other women in Sparta; and what was still more strange, she had once been as ugly as she now was beautiful. For her nurse, seeing how ill-favoured she was, and how sadly her parents, who were wealthy people, took her bad looks to heart, bethought herself of a plan, which was to carry the child every day to the temple of Helen at Therapna, which stands above the Phoebeum, and there to place her before the image, and beseech the goddess to take away the child's ugliness. One day, as she left the temple, a woman appeared to her, and begged to know what it was she held in her arms. The nurse told her it was a child, on which she asked to see it; but the nurse refused; the parents, she said, had forbidden her to show the child to any one. However the woman would not take a denial; and the nurse, seeing how highly she prized a look, at last let her see the child. Then the woman gently stroked its head, and said, "One day this child shall be the fairest dame in Sparta." And her looks began to change from that very day. When she was of marriageable age, Agetus, son of Alcides, the same whom I have mentioned above as the friend of Ariston, made her his wife.
Now it chanced that Ariston fell in love with this person; and his love so preyed upon his mind that at last he devised as follows. He went to his friend, the lady's husband, and proposed to him that they should exchange gifts, each taking that which pleased him best out of all the possessions of the other. His friend, who felt no alarm about his wife, since Ariston was also married, consented readily; and so the matter was confirmed between them by an oath. Then Ariston gave Agetus the present, whatever it was, of which he had made choice, and when it came to his turn to name the present which he was to receive in exchange, required to be allowed to carry home with him Agetus's wife. But the other demurred, and said, "except his wife, he might have anything else": however, as he could not resist the oath which he had sworn, or the trickery which had been practised on him, at last he suffered Ariston to carry her away to his house.
Ariston hereupon put away his second wife and took for his third this woman; and she, in less than the due time—when she had not yet reached her full term of ten months—gave birth to a child, the Demaratus of whom we have spoken. Then one of his servants came and told him the news, as he sat in council with the Ephors; whereat, remembering when it was that the woman became his wife, he counted the months upon his fingers, and having so done, cried out with an oath, "The boy cannot be mine." This was said in the hearing of the Ephors; but they made no account of it at the time. The boy grew up; and Ariston repented of what he had said; for he became altogether convinced that Demaratus was truly his son. The reason why he named him Demaratus was the following. Some time before these events the whole Spartan people, looking upon Ariston as a man of mark beyond all the kings that had reigned at Sparta before him, had offered up a prayer that he might have a son. On this account, therefore, the name Demaratus was given.