Prometheus had stolen fire from heaven and gave it to mortal man. Zeus disapproved of his philanthropic act. To punish Prometheus, Zeus commanded that he be chained to a mountain in the Caucasus range.
Hephaestus was supposed to carry out this edict. Much against his will, he chained Prometheus to the mountain, so that he was exposed to the inclement elements. Strength and Force accompanied him. Strength had to prod the reluctant Hephaestus to obey the edict of Zeus.
After Hephaestus finished his task and left the scene with his two companions, Prometheus began to lament his fate. His soliloquy was interrupted by the entrance of the chorus, a bevy of winged ocean nymphs.
The chorus of nymphs sympathized with him. They pointed out that Zeus was a young god who had recently gained power. They complained that he had proved to be a cruel despot.
Prometheus said that he wished Zeus had sent him to Tartarus instead of punishing him in the open air, where all his foes could see his torments and mock him. In reply, the chorus assured Prometheus that all the gods pitied him, except for Zeus. None of them would be inclined to mock him.
As he contemplated the tyranny of Zeus, Prometheus had one consolation. Zeus was in danger of losing his power, and only the advice of Prometheus could save him. Prometheus was determined not to help Zeus until he set him free and made amends for his cruelty.
The chorus asked Prometheus to tell them why he was being punished. In reply, Prometheus first pointed out that he had helped Zeus in his war against the older gods. Prometheus claimed that his advice was the crucial factor in the victory of Zeus and the younger gods. Once in power, Zeus became a cruel ruler. He wanted to crush mortal men and replace them with a new race. Because Prometheus frustrated this heartless project, Zeus subjected him to the horrible punishment that the ocean nymphs were witnessing.
Prodded by the chorus, Prometheus mentioned further benefits that he had conferred on mankind. When men were cowed by the fear of death, Prometheus gave them hope and the gift of fire, from which they would learn many useful arts.
While Prometheus was conversing with the chorus, Okeanus, the father of the assembled ocean nymphs, entered the scene. He sympathized with Prometheus and wanted to help. Okeanus even suggested that he might be able to persuade Zeus to free Prometheus.
Prometheus was grateful, but urged Okeanus not to attempt anything on his behalf. It would do no good, and Okeanus might suffer if he got involved. Prometheus felt sorry for his kinsman Atlas, whom Zeus had compelled to bear the pillars of heaven and earth on his shoulders. He also pitied Typhon, whom Zeus had struck with a thunderbolt and who lay prostrate under Mount Etna. He did not want Okeanus to suffer a similar fate.
Okeanus left the scene, and a choral interlude followed. The chorus expressed their own grief over the sufferings of Prometheus and pointed out that the race of mortals also grieved over his sufferings. The choral section concluded with a sympathetic description of the sufferings of Atlas.
Prometheus then told the chorus about all the good that he had done. He briefly alluded to the benefits that he had conferred upon the younger gods when they were fighting the older Titans. He then elaborated on the way he had helped mankind. They were like babes before he taught them to think. They did not even know how to make houses of brick, but dwelt in holes like a swarm of ants.
To improve their lot, Prometheus showed them how to use the stars to compute the seasons. He taught them numbers and letters. He taught them how to use chariots and ships for transportation. He taught them how to treat sicknesses. He taught them many modes of prophecy, such as how to interpret dreams and the flight of birds. He opened their eyes to the wealth that lay in the bosom of the earth: bronze, iron, silver, and gold.
As the dialogue with the chorus continued, Prometheus told the chorus that after undergoing much suffering, he would escape his bonds. He stated that even Zeus could not alter the decrees of Fate. By mentioning the Erinyes, he hinted that Zeus might not fare too well at some indefinite future date. Though prodded by the chorus, Prometheus refused to elaborate. It was a dread secret, and the time to talk about it had not yet come.
In a short interlude, the chorus expressed the hope that Zeus would never be angry with them. They felt that it was wise to respect the power of Zeus rather than imitating Prometheus, who resisted the will of Zeus because of his excessive love for mortals, who were powerless to help him.
The chorus concluded on a cheerful note. They remembered the wedding of Prometheus and their own sister Hesione. On that joyous occasion, they had sung wedding hymns for the happy couple.
Io entered the scene. She was wandering over the earth, chased by a gadfly that repeatedly stung her and haunted by the shades of Argos. A pair of horns adorned her head.
At her request, Prometheus introduced himself. Io did not need to tell Prometheus who she was because Prometheus already knew that she was Io, the daughter of the river god Inachus. He also knew that Zeus loved her and that Hera consequently hated her. He explained to the chorus that Io was their relative [since Inachus was a son of Okeanus].
At the request of the chorus, Io explained why she was being tormented. Zeus had come to her in seductive dreams. He urged her to go to Lerna and become his bride. [Lerna was a swamp at the mouth of the Inachus River near the city of Argos.]
She eventually told her father about her dreams. To learn the will of the gods, Inachus visited the oracles at Dodona and Delphi, but the language of these oracles was not intelligible. Finally, Inachus received a clear command. He was ordered to expel Io from her home and from her country. If he disobeyed, the thunderbolt of Zeus would destroy his race. So he reluctantly obeyed the cruel command.
Just as animals were occasionally consecrated to a god and allowed to stray at large, so Io was consecrated to Zeus. Horns grew on her head, her mind assumed a bovine mentality, and Argos followed her until he was deprived of life. A gadfly repeatedly stung her and chased her from land to land.
After Io finished her account, Prometheus warned her that she would face further trials in the future. He told her that Zeus was imposing these wanderings on her in an effort to gain her embraces. Zeus was proving to be a bitter suitor.
Prometheus then told her what would happen to her in the future. In the course of her wanderings, she would cross a strait from Europe into Asia. This strait would be called the Bosporus in commemoration of her crossing. She would also travel in lands inhabited by unfriendly races, such as the Scythian nomads. She would also reach lands inhabited by fearful monsters, such as the gorgons. She would have to beware of the gryphons and the one-eyed Arimaspians. Her wanderings would end in the land of the Nile – a land that her progeny would inhabit.
Prometheus mentioned a few things that Io had experienced in the past. He did so to demonstrate the accuracy of his knowledge to Io and to the chorus. Since he could speak accurately about events that he had not witnessed, Io would know that she could depend on everything that Prometheus told her.
In her previous wanderings, Io had come to the oracle of Zeus at Dodona. Here the oracle told her that she was the spouse of Zeus. She was afflicted with frenzy and hastened away. She came to a body of water which was called the Ionian Sea because of her.
After thus demonstrating the accuracy of his knowledge, Prometheus returned to her future experiences in the land of the Nile. By a simple touch that worked no terror, Zeus would restore her to her right mind. She would then bear a child named Epaphus, born by the touch of Zeus.
During the course of his conversation with Io, Prometheus elaborated on the threat faced by Zeus. In the future, he would attempt to wed a virgin, whom Prometheus does not name. [Her name was Thetis, the daughter of Nereus.] If he succeeded, they would have a son who would be mightier than Zeus, and the reign of Zeus would come to an end. Prometheus could save Zeus by giving him a timely warning, but he declared that he would not do so unless Zeus released him from his bonds.
Prometheus also informed Io that one of her descendants would free him. [It would be Hercules. Prometheus did not name him, but mentioned that he would be the thirteenth generation of Io’s descendants.]
After Prometheus gave Io further information concerning her descendants, the gadfly began to sting Io, and frenzy seized her mind. As a result, her conversation with Prometheus came to an end.
Hermes entered the scene. Zeus somehow had learned what Prometheus was saying about the disaster that he would suffer in the future. Zeus wanted to know what marriage would be dangerous to him, and who would depose him. So he sent Hermes to elicit this information from Prometheus.
When Prometheus categorically refused to provide the desired information, Hermes told Hercules that Zeus would send dire calamities upon him. Zeus would crush the rocks and hide the carcass of Prometheus. Afterwards, Prometheus would be brought to light once more, and an eagle would feast upon him, consuming his liver.
Hermes urged Prometheus to give up his obstinate pride, and the chorus of ocean nymphs seconded the plea of Hermes.
When Prometheus persisted in his defiance, Hermes warned the ocean nymphs to leave, lest they share in the calamities that were about to fall upon Prometheus. The ocean nymphs refused to forsake the stricken Titan.
As thunder and lightning descended from heaven, the drama came to an end.
Note that Aeschylus’ account of Io myth differs from other ancient accounts. In such ancient writings as pseudo-Apollodorus, Zeus was committing adultery with Io, and Hera was about to discover his infidelity, so Zeus transformed Io into a white cow to escape detection. Hera knew what Zeus had done and asked him to give her the white cow. Zeus had to comply. Hera appointed a hundred-eyed creature named Argus to guard her, but Hermes killed Argus. Then Hera sent a gadfly to persecute Io. Still in the form of a cow, she fled from country to country, until she reached Egypt. Here Hera allowed Zeus to restore Io to her original form on the condition that he pay no further attention to her. Io then gave birth to Epaphus.
In contrast to this more common version of the myth, Aeschylus does not turn her completely into a bellowing cow, but only gave her a pair of horns and altered her mind. Moreover, on the reason why the gadfly was forcing Io to wander far and wide, Aeschylus was ambiguous. On the one hand, he ascribed her miseries to the jealousy of Hera. On the other hand, he stated that Zeus was imposing these wanderings on her in an effort to gain her embraces.
There also seems to be a difference on when Epaphus was conceived. Before commenting on this, I would have to examine crucial words in the Greek text, which I do not have at my disposal. The foregoing article is based on an English translation of Prometheus Bound presented online by Classical Authors.