This was a startling theme. At Siwah, wrote Callisthenes, 'the priest told Alexander expressly that he was son of Zeus', and on his return to Memphis he was met by envoys from Greek oracles in Asia Minor, one of whom, wrote Callisthenes, had broken its silence of the past hundred and fifty years in order to greet the new avenger of Persian wrongs as Zeus's son. Six months later, wrote Callisthenes, on the verge of his greatest battle Alexander prayed to the gods to help him 'if he were indeed sprung from Zeus'; Callisthenes wrote to please Alexander and he can only have stressed this divine sonship because it was to Alexander's liking. Other contemporaries followed suit and the connection between the visit to Siwah and the sonship of god remained a lively one; Seleucus, Alexander's eventual successor in Asia, actually developed a story thirty years later that he had visited a Greek oracle in his Asian kingdom and been similarly recognized as the begotten son of Apollo. To those who had known Alexander personally, the scene at Siwah had lost none of its credibility.

Later, Alexander's divine sonship was wrongly derived from the answers which he received inside Amnion's shrine, but as he never revealed what he asked or heard, it cannot have been these which first gave the cue to Callisthenes. When he wrote that the 'priest had expressly told Alexander he was son of Zeus', the priest must have done this publicly, where Callisthenes could hear him, presumably therefore in his greeting on the temple steps. Either the priest may have heard that Alexander was the new Pharaoh and greeted him by 'son of Amun', one of the five Egyptian royal titles, which Callisthenes then translated as 'son of Zeus' for his Greek audience. Or, more probably, he intended to address Alexander in Greek as 'my boy' (o paidion),but erred and said 'o paidios'instead, which sounded to the listening Macedonians like the two words 'pat diosor 'son of Zeus'. This slip of the tongue was widely believed in antiquity, and as Greeks believed such fortunate errors at a solemn moment to be favourable omens, Alexander would have taken it to be another sign from heaven. Frequent visits from Greek envoys had ensured that many of the temple staff could manage a few words of Greek, but there is no reason to suppose that the high priest's pronunciation was ever perfect.

The priest's precise greeting matters very much less than what Alexander wished to be believed of it; according to his own historian, he was the begotten son of Zeus as a result of his visit, and it is very arguable how and why this belief had arisen. Egyptian kingship, at first sight, seems to promise an explanation; in Upper Egypt, the Pharaoh had always been worshipped as 'son of Amun' and whenever the dynasty of the Pharoahs changed, whether for the usurping Tuthmosis III, the native Saites or the invading Persians, the new line had been fitted into the past by this myth of divine fatherhood. Psamtik I, more than three hundred years before Alexander, had begun a new line, but instead of stressing his earthly mother, perhaps because she was Libyan, he publicized his sonship of Amun 'who has begotten me for himself, to please his heart', because Amun was a father whom he could share with the native Pharaohs before him. Like Psamtik, Alexander was founder of a new and foreign line; his sonship of Amun must have been emphasized by the priesthood to suit the old traditions and Alexander's staff may have picked it up, translating Amun into Zeus, as had always been Greek custom. Alexanders sonship, then, would have been known before he set out for Siwah; when he returned to Memphis, he was met by envoys from Asian Greek oracles with messages to confirm his divine father, and if the 'son of Zeus' was nothing more than the Pharaoh explained in Greek terms they could have been forewarned before he left Alexandria to travel into the desert.

This Egyptian influence may well be a part of the truth: it is not necessarily the whole of it. Alexander's lasting reverence for Zeus Ammon suggests some sort of a revelation had indeed taken place at Siwah, and there is no room for this if his sonship was only a Greek translation of a Pharaoh's title; he was probably Pharaoh by the time he reached Siwah, and whether or not he had been crowned officially in Memphis, he would already be familiar with his new royal titles: he may not have understood them fully, but he had certainly heard them, perhaps from native priests.

Egyptians at his court or from the Greeks who had long lived near the site of his new Alexandria. True, a queen of the Ptolemies was later honoured as 'child of Ammon', simply as a loose politeness to match her official link with the Pharaohs' Amun through her husband; the Roman emperor Vespasian was perhaps feted as 'son of Ammon' when he entered Egypt as Pharaoh. But those mild parallels for future western rulers belong later, when Egypt had been hellenized and when Alexander had made the sonship of Ammon famous. Only in one posthumous Greek statue is Alexander ever shown with the crown and symbols of a Pharaoh; none of his friends or historians is known to have alluded to his kingship in Egypt at any other time, and it did not influence his life, any more than later, when he became king of Persia, did he show any grasp or concern for the equally holy doctrines of the god Ahura Mazda. And yet Siwah and his sonship of Zeus were to remain lively themes until the very last year of his reign when Egypt had been forgotten; it is possible to look for a deeper source and it lies, moreover, near to home.

Among Greeks also, to be 'sprung from Zeus' was a mild and intelligible claim. The first Macedonian, for example, was believed to have been Zeus's son; 'Zeus-born' was a frequent description of Homer's epic kings, and in Alexander's day, the foreign royalty of Cyprus maintained that Zeus stood at the head of their family-tree, while the kings of Sparta could be described as the seed of Zeus. Descent from a god could also be used figuratively: Plato the poet and philosopher was praised as a 'son of Apollo, by his cleverest Athenian pupil, but this may have meant no more than that Plato too had a divine mastery of the arts. But Alexander's descent from Zeus was described by the Greek word genesis,and this most naturally meant that he was Zeus's begotten son, not his distant descendant.

Surprisingly, there was a Greek precedent for this claim too. In Homer's poems, several kings and heroes had a god as their acknowledged father, and this bluest of all blue blood was a point of especial honour for their reputations, while in Greek Sicily, some ten years before Alexander was born, this heroic fancy had found a true expression. Dionysius II, ruler of Syracuse, had maintained that he was fathered by Apollo, and had composed a verse inscription for his statue to stress this publicly and unmistakably. Without the influence of Egypt, therefore, a claim to be begotten by a god could be shared and understood by Greeks and it is fair to consider whether Alexander had drawn his new sonship as much from his own Greek background as from a pharaonic title which he scarcely understood.

A close attachment to Zeus was in no way remarkable for him. His father Philip had been acknowledged as specially protected by Zeus, and on coins, Philip's bearded features had shown a clear resemblance to the king of the gods. Macedonian kings numbered Zeus among their ancestors, and they may have worn his symbolic aegis or goat-skin cloak in daily life, just as Alexander was shown wearing it on posthumous statues in Egypt, and his friend Ptolemy was shown with it on coin portraits during his lifetime as Pharaoh. In his sacrifices and dedications, Alexander repeatedly honoured Zeus, who remained the most important god in his life: when, in his last months, he received envoys from Greek temples all over the Mediterranean and admitted them to his presence in order of their importance, the representatives of Olympian Zeus came first, those of Ammon at Siwah second, for he still regarded Ammon as his own Greek Zeus in Libyan form. It is not true that after Siwah, Alexander believed himself to be son of a foreign Libyan god, whom he honoured before all the Greek gods of his childhood until the day he died; rather, at Siwah, a Libyan oracle which spoke for the Greek Zeus had supported the belief that he was the Greek god Zeus's son. He had been familiar with Zeus, if not Ammon, long before he journeyed to Siwah, and it is possible, therefore, that Amnion's oracle had only confirmed a belief which had long been growing on him. A fortunate slip of the priest's tongue, against his mystical role as the new Pharaoh, might have turned suspicion into conviction from Siwah onwards for the rest of his life.