What is the theme in Act III, Scenes 4-5 of Romeo and Juliet?

The major themes of Act III, Scenes 4 and 5 are love and how the social world interferes with the love of Romeo and Juliet. 

In Scene 4, Lord Capulet attempts to show his love for his daughter by promising her to Count Paris, who has been interested in Juliet from the beginning of the play. Capulet believes it will be good for the family to hold a wedding after the sudden death of Tybalt, Juliet's cousin. He is quite excited about the prospect of a marriage and is certain Juliet "will be ruled." Of course, Capulet knows nothing about Romeo and is quite unaware that Romeo is in Juliet's bedroom this very night for the couple's honeymoon. The lovers are unaware that once again, as in Act III, Scene 1, the social world of Verona will interfere with their love.

Scene 5 opens with Romeo and Juliet alone in the girl's bedroom. Juliet doesn't want Romeo to leave so she says it is the nightingale, the symbol for the night, singing outside her bedroom. It is actually the lark, symbol of the day, as Romeo concludes. The scene ends with the two pledging their love and Romeo guaranteeing he will write to her as often as possible. He says,

Farewell.
I will omit no opportunity
That may convey my greetings, love, to thee.

In the remaining parts of this scene Juliet's obligations to society are magnified as her father and mother come to her with their decree that she marry Paris. Capulet goes into this scene certain Juliet will be overjoyed about his news. What he finds, however, is a defiant daughter. She asks him to postpone the wedding but he refuses and threatens to disown her if she doesn't go through with it. Neither her mother nor the Nurse offer any sympathy. The Nurse even suggests that Juliet forget Romeo and marry Paris. Juliet is distraught and the interference of society leads directly to her suicide as she seeks advice from the Friar who devises the unsuccessful plan for her to fake her death.