Identity
Identity is a major theme throughout the film. It is the main theme in fact, as Ernest is the name that everyone is seeking and yet, no one actually has this name. Jack has made himself into another man in London, name Ernest. And Alge pretends to be Ernest to Cecily in order to marry her. Both Cecily and Gwendolen desire to be married to a man named Ernest, whose name sounds so musical to them and exciting, whereas Jack and Alge do not.
Turns out that Jack was named after his father who he never knew, his name...Ernest. And with that he claims his identity, family and his wife.
Class
Class is a major theme in this film as we see that Jack has asked for Gwendolen's hand in marriage to which her mother, Lady Bracknell takes him through a wringer of questions. The point is that she must know if he is from a reputable family, has money and property and the ability to provide for her daughter. She must approve of his standing in order to keep her family's name in the upper echelon of society.
Courtship
The process of courting a woman is much different than in today's time. Jack and Alge go through a rather--so it seems, process of asking for the woman's hand in marriage and they say yes. But, Alge, unbeknownst to him has been writing to Cecily for quite some time, and Jack and been wooing Gwendolen as well for quite a while. The process to get close was intricate in that there was very little forward speech to the one you would propose to, it was a very calculated and arranged courtship that would lead to the couple being married and we see the end result of that in this film.
