Apollonius was born around the year 3 CE in Tyana, a Greek city in the Roman province of Cappadocia, in the highlands of what is now southern Turkey. His family was wealthy and respected, and he received the finest education available, studying grammar and rhetoric at Tarsus, the city where the apostle Paul would later be born, and then medicine at the temple of Asclepius at Aegae, the healing sanctuary on the coast where the sick came to sleep in the god's precinct and receive dreams that would cure their ailments. But it was Pythagoras, the philosopher who had lived six centuries earlier on the island of Samos and in southern Italy, who captured his soul. Apollonius adopted the Pythagorean way in its fullest form. He ate no meat, drank no wine, wore only linen garments instead of wool, and took a vow of celibacy. He believed that the gods, being the most beautiful beings in existence, could not be influenced by prayers or sacrifices, but could be reached only through the intellect, the nous, which was the divine spark within every human soul.

When he was still a young man, Apollonius renounced his inheritance and set out to wander the world. He was accompanied by a small band of disciples, the closest of whom was Damis, a native of Nineveh in Syria who met him at Hierapolis Bambyce and became his lifelong companion. Damis kept a diary of their travels, or so the later biographer Philostratus claimed, and from those notes the world learned of Apollonius' extraordinary journey. They travelled through Mesopotamia to Babylon, where Apollonius conversed with the Magi. They crossed into India and reached Taxila, the capital of the Indo-Parthian king Phraotes, where Apollonius debated with the Brahmins and the naked philosophers called gymnosophists. In Egypt he visited the pyramids and the temples of the Nile. In Ethiopia he spoke with the sages of the south. Everywhere he went, he taught the same doctrine: reject animal sacrifice, live simply, cultivate the intellect, and know that the soul is immortal and destined to be reborn until it achieves perfection.

But Apollonius was not merely a philosopher. He was a wonder-worker. In Ephesus, he warned the citizens that a plague would strike them in the form of a wretched beggar. When the pestilence arrived, the people remembered his words and sought his counsel. Apollonius told them to stone the beggar to death. They did so, and when they lifted the pile of stones, they found not a man but a black dog, the demon that had been spreading the disease. In another city, a Roman consul's daughter died on the day of her wedding. Apollonius touched her body and she returned to life, though Philostratus himself admitted uncertainty about whether she had truly been dead or merely in a death-like trance. In Corinth, he stopped his former student Menippus from marrying a woman who was not a woman at all but a lamia, a vampire spirit who had created an illusion of wealth and beauty. Apollonius made the banquet and the guests disappear, exposed the creature's true form, and saved Menippus from destruction.

The most dangerous journey Apollonius ever made was to Rome. The emperor Nero had banned all philosophers from the city, fearing their influence over public opinion. Apollonius entered anyway, walking through the gates in his simple linen robe with his staff of wild olive in his hand. He was arrested, questioned, and released, for the authorities could find no crime in a man who owned nothing and threatened no one. Years later, under the emperor Domitian, the danger returned. Domitian was a tyrant who demanded to be addressed as "lord and god," and he saw in Apollonius a rival whose reputation for wisdom and miracle-working challenged his own claim to divinity. The emperor had Apollonius arrested on charges of conspiracy, human sacrifice, and predicting a plague by magical means. He was brought to Rome in chains and thrown into prison.

The trial was one of the most dramatic confrontations between philosophy and power in Roman history. Apollonius stood before Domitian in the imperial court and answered every accusation with calm logic and devastating wit. When asked why he had conspired against the emperor, he replied that a philosopher who owned nothing could not desire a throne. When asked about his magical powers, he said that his only power was the power of foresight, which came from purity of life, not from spells. The court applauded his defence. Domitian, unable to convict him by argument, ordered his execution anyway. But when the guards came to take him to his death, they found the cell empty. Apollonius had simply vanished. He reappeared that same day in Puteoli, on the Bay of Naples, three days' journey from Rome, where he met Damis and told him what had happened. He had not escaped, he said. He had never been truly imprisoned, for the body that the emperor thought he held was merely an appearance, and the real Apollonius was beyond the reach of chains.

After this miracle, or this escape, or this demonstration of the philosopher's freedom from the body, Apollonius continued to travel and teach. He established a school at Ephesus, where he lived out his final years. The manner of his death is as mysterious as the rest of his life. Philostratus records several versions. Some said he died at Ephesus in the care of two servant girls, aged somewhere between eighty and a hundred years, still youthful in body and mind. Others said he entered the temple of Athena at Lindos on the island of Rhodes and disappeared. The most famous account tells of a night in Crete, when he visited the sanctuary of Dictynna, the goddess of the hunt. The guards bound him, but at midnight the doors of the sanctuary opened of their own accord, and from within came the voices of maidens crying, "Proceed from earth! Proceed to heaven! Proceed!" When the doors were opened, Apollonius was gone. His followers believed he had been taken up into heaven, and for centuries after his death, people reported seeing him in visions, still walking the roads of the empire in his linen robe.