Although Alexander the Great was the son of king Philip of Macedonia and queen Olympias, he claimed to be the son of a god. As a consequence, stories about his miraculous procreation were needed. In section 2-3 of his Life of Alexander, the Greek author Plutarch of Chaeronea shows us what was invented.
The translation was made by Mr. Evelyn and belongs to the Dryden series.
The birth of Alexander
[2.2] His father Philip, being in Samothrace, when he was quite young, fell in love there with Olympias, in company with whom he was initiated in the religious ceremonies of the country, and her father and mother being both dead, soon after, with the consent of her brother, Arymbas, he married her.
[2.3] The night before the consummation of their marriage, she dreamed that a thunderbolt fell upon her body, which kindled a great fire, whose divided flames dispersed themselves all about, and then were extinguished.
[2.4] And Philip, some time after he was married, dreamt that he sealed up his wife's body with a seal, whose impression, as be fancied, was the figure of a lion.
[2.5] Some of the diviners interpreted this as a warning to Philip to look narrowly to his wife; but Aristander of Telmessus,note[Telmessus, modern Gurice near Bodrum, was a town in Caria, famous for its oracle and seers. Aristander accompanied Alexander and was present when Alexandria was founded.] considering how unusual it was to seal up anything that was empty, assured him the meaning of his dream was that the queen was with child of a boy, who would one day prove as stout and courageous as a lion.
[2.6] Once, moreover, a serpent was found lying by Olympias as she slept,note[The symbolism is not really understood. Snake cults were known on the Balkans (e.g., Glykon), but this time, an Egyptian god was believed to be the father, not a god from the Balkans. To make things more complex, the Roman historian Livy tells the same story about the Roman general Publius Cornelius Scipio Africanus (more...).] which more than anything else, it is said, abated Philip's passion for her; and whether he feared her as an enchantress, or thought she had commerce with some god, and so looked on himself as excluded, he was ever after less fond of her conversation.
[2.7] Others say, that the women of this country having always been extremely addicted to the enthusiastic Orphic rites, and the wild worship of Bacchus [...], imitated in many things the practices of the Edonian and Thracian women about Mount Haemusnote[Mount Haemus is the ancient name for the Balkan range. These cults were Thracian in origin.] [...];
[2.9] and that Olympias, zealously, affecting these fanatical and enthusiastic inspirations, to perform them with more barbaric dread, was wont in the dances proper to these ceremonies to have great tame serpents about her, which sometimes creeping out of the ivy in the mystic fans, sometimes winding themselves about the sacred spears, and the women's chaplets, made a spectacle which men could not look upon without terror.
[3.1] Philip, after this vision, sent Chaeron of Megalopolis to consult the oracle of Apollo at Delphi, by which he was commanded to perform sacrifice, and henceforth pay particular honor, above all other gods, to Ammon;note[Ammon was considered to be the Egyptian equivalent of the Greek supreme god Zeus. It is obvious that this story was invented after Alexander's visit to Ammon's oracle.]
[3.2] and was told he should one day lose that eye with which he presumed to peep through that chink of the door, when he saw the god, under the form of a serpent, in the company of his wife.note[Philip lost his eye in battle.]
[3.3] Eratosthenes says that Olympias, when she attended Alexander on his way to the army in his first expedition, told him the secret of his birth, and bade him behave himself with courage suitable to his divine extraction.
[3.4] Others again affirm that she wholly disclaimed any pretensions of the kind, and was wont to say, "When will Alexander leave off slandering me to Hera?"note[Hera was Zeus' wife. Olympias' joke may be authentic.]
[3.5] Alexander was born the sixth of Hecatombaeon,note[The first month of the year, theoretically starting on the first new moon after the summer's solstice. This could mean that Alexander was born on 20 July 356. Unfortunately, the astronomical, religious and civil calendars did not coincide in the fourth century; as aconsequence, it is impossible to give the date of Alexander's birth.] which month the Macedonians call Lous, the same day that the temple of Artemis of Ephesus was burnt:note[The famous temple of Artemis (one of the Seven Wonders of the Ancient World) had been set afire by a man named Herostratus, who declared that his aim had been to become famous.]
[3.6] which Hegesias of Magnesia makes the occasion of a conceit, frigid enough to have stopped the conflagration. The temple, he says, took fire and was burnt while its mistress was absent, assisting at the birth of Alexander.
[3.7] And all the Eastern soothsayers who happened to be then at Ephesus, looking upon the ruin of this temple to be the forerunner of some other calamity, ran about the town, beating their faces, and crying that this day had brought forth something that would prove fatal and destructive to all Asia.
[3.8] Just after Philip had taken Potidaea, he received these three messages at one time, that Parmenion had overthrown the Illyrians in a great battle, that his race-horse had won the course at the Olympic games, and that his wife had given birth to Alexander;
[3.9] with which being naturally well pleased, as an addition to his satisfaction, he was assured by the diviners that a son, whose birth was accompanied with three such successes, could not fail of being invincible.