Marriage
Although the broad theme in the play is marriage, unhappy marriage is actually a more accurate description since Mariam's marriage is clearly miserable. It is also one that leaves her truly conflicted. She remembers that she must have loved Herod once, but she also resents and hates him for murdering her brother and father. This makes it difficult for her to decide how to feel about his believed death. The marriage is seen as a troublesome and conflict-ridden one, with Herod a dictatorial husband who expects his wife to accede to his every demand. Mariam is caught between a rock and a hard place in that she is torn between her duty as a wife, and the reality of her feelings of resentment towards her husband.
The theme of marriage also reflects the main theme of Cary's own life at the time of her writing the text; she, too, was torn between wifely duty - remaining in the Church of England because her husband wished her to do so - and her own wish to convert to Roman Catholicism.
Female Oppression
Society in Herod's day, being much like society at the time of the play was written, had many laws that treated women as second class citizens, preventing them from instigating a divorce and giving the husband the sole right to petition to dissolve a marriage. This was the case in Cary's own life too, and it is the case for all of the women in the play. Salome is not going to accept the status quo and much of the text deals with her determination to divorce her husband; whilst the play ends before we find out if she was successful or not, the theme is nonetheless strong throughout.
Ruling With An Iron Fist
Herod's death throws up a variety of responses that are surprising given that most citizens mourn their monarchs when they die - or are believed to have died. In Herod's case, most of the characters seem to be able to let out a large sigh of relief. They seem to be joyful because he is not going to be coming back to rule them. This is not the typical reaction from subjects who admire and love their king. The truth of the matte is that Herod is a tyrant, a dictator who rules everyone with an iron fist. Once they believe him to be gone, they are free to pursue the people and interests that they have had all along but have been too frightened to. The theme of ruling in this way also shows that a ruler will never get the best of their people by terrorizing people. It also shows that Herod's rule is more bloody than the Bible account leads us to believe.
Infidelity
Salome, the real main character, is cheating on her husband and wants to divorce him so that she can marry her lover. She no longer love her husband and wants to humiliate him as a punishment for not having divorced her yet. Her infidelity is also the vehicle for presenting other themes, such as the oppression of women, and also showing what a nasty character he actually is.
