Everyone who enters into marriage places themselves under the governance of Hera, the goddess of marriage, wife to Zeus, queen of Olympus and all the gods.
By swearing to the vows of marriage, Jason binds himself to Medea forever.
He swears to Hera who had been his constant benefactor, to uphold the trust she held more sacred than any other.
Hera blessed them with children, and as a father Jason is obligated to look after their interests, to the greatest extent of his capabilities.
When Jason announces his intention to marry Glauce, daughter of Creon, king of Corinth,
Medea is betrayed, both in her person, and in her children.
The oaths that Jason swore as husband, and father, are holy obligations. By even entertaining the offer of marriage to Glauce, Jason has abrogated his obligation. When Jason announces that he has accepted the offer, Medea is right to feel that both she and her children have been irreparably wronged.
They are harmed by Jason's licentious union with the princess of Corinth. Any extramarital relationship that Jason has with the princess are a threat to her and her children!
In the eyes of Hera, this is a criminal violation of their marriage.
On account of these crimes Medea speaks out to the people of Corinth, in defense of herself, her children and their rights. She berates Jason, upbraids the king, and denounces the princess. Her speeches are effective. The people side with her, and this embarrasses the royal family.
I hear a cry of grief and deep sorrow. In piercing accents of misery she proclaims her woes, her ill starred marriage and her love betrayed. The victim of grievous wrongs, she calls on the daughter of Zeus, even Themis, lady of Vows, who led her through the night by difficult straights across the briny sea of Hellas.[i]
Medea speaks out against her plight. She recounts her instrumental role in Jason’s accomplishments, and by invoking Themis, daughter of Zeus, who oversees the sanctity of vows, she makes a legal argument against Jason, Creon, and Glauce.
Medea presses her case in public, and this is contrary to the customs of ancient Greece.
In Euripides day, women did not lead a public life. They were strictly censured by their husbands. As was most often the case, a woman, even a princess, would not be granted any legal recourse unless they were represented by some influential male in their society.
Medea had no such representation. As a result of this breach of etiquette, and decorum Medea is threatened with exile by the king if she does not recant.
She does not, even while knowing that exile in a foreign land would mean certain disaster for her, and her children.
Medea's is courageous in her search for justice, demonstrating once again her innate heroism.