Before starting on his missionary activities—he was probably by far the greatest traveller of his time—he took the vow of silence for five years. After this, he travelled from place to place making the acquaintance of temple priests and heads of the religious communities, endeavouring always to bring back the public cults to the purity of their ancient traditions and to suggest improvements in the practices of the private brotherhoods, the most important part of his work being devoted to those who were followers of the inner life. _Public_ instruction in ethics and practical life he never gave until after the middle of the day, “for,” he said, “those who live the inner life should on day’s dawning enter the presence of the gods, spending the time till midday in giving and receiving instructions in holy things.” His Indian expedition, from which his friends and disciples endeavoured to dissuade him, he undertook, as he stated, on the advice of his inner monitor, starting his perilous undertaking entirely alone, and so continuing until he made the acquaintance of Damis at Nineveh. There is some doubt as to the date of Apollonius’s birth, but an allusion by Philostratus makes it appear that he was quite a young man at the time of his Indian expedition, and as he apparently did not commence his five years’ vow of silence till after he came of age, we must assume that he was somewhere between twenty-six and thirty at the commencement of this undertaking. Treadwell dates the Indian travels as from 41 to 54 A.D. If this is approximately accurate we may assign his birth-date to the second decade of the first century of the Christian era. Assuming this to be the case, he was presumably over eighty years old at the time of his death, which occurred about 98 A.D. Damis had been his almost inseparable companion from the time when he first met him at Nineveh. It seems to have been a case of something akin to “love at first sight,” for the Assyrian was seized at once with an enthusiasm for the nobility of Apollonius’s character, which was blent with a natural and even dog-like affection. At the last, however, his companion was not with him, and there is some mystery as to the exact place and occasion of his death. He sent Damis away when the expected time approached, on the pretext of entrusting him with a confidential letter to the Emperor Nerva, so that it may be said of him, as it was of Moses, “No man knoweth his burial place unto this day.”