Constantius died in 361; but Themistius, as a philosopher and non-Christian, naturally retained the favour of Julian, who spoke of him as the worthy senator of the whole world, and as the first philosopher of his age. The Suda states that Julian made Themistius prefect of Constantinople; but this is disproved by the speech delivered by Themistius, when he was really appointed to that office under Theodosius. Shortly before the death of Julian in 363, Themistius delivered an oration in honour of him, which is no longer extant, but which is referred to at some length by Libanius, in a letter to Themistius. In 364 he went, as one of the deputies from the senate, to meet Jovian at Dadastana, on the border of Galatia and Bithynia, and to confer the consulate upon him; and on this occasion he delivered an oration, which he afterwards repeated at Constantinople, in which he claims full liberty of conscience to practice any religion. In the same year he delivered an oration at Constantinople, in honour of the accession of Valentinian I and Valens, in the presence of the latter. His next oration is addressed to Valens, congratulating him on his victory over Procopius in June 366, and interceding for some of the rebels; it was delivered in 367. In the next year he accompanied Valens to the Danube in the second campaign of the Gothic war, and delivered before the emperor, at Marcianopolis, a congratulatory oration upon his "Quinquennalia", 368. His next orations are to the young Valentinian II upon his consulship, 369, and to the senate of Constantinople, in the presence of Valens, in honour of the peace granted to the Goths, 370. On March 28, 373, he addressed to Valens, who was then in Syria, a congratulatory address upon the emperor's entrance on the tenth year of his reign. It was also while Valens was in Syria, that Themistius addressed to him an oration by which he persuaded him to cease from his persecution of the Catholic party. In addition to these orations, which prove that the orator was in high favour with the emperor, we have the testimony of Themistius himself to his influence with Valens.