Ophelia is torn between two competing impulses. On the one hand, she is loyal to her father. Polonius doesn't want Ophelia to have anything to do with Hamlet; he thinks that Hamlet doesn't really respect her and just looks at her as an object of lust. In common with most fathers of the time Polonius puts his daughter on a pedestal, idealizing her as a pure, unsullied virgin whose honor and integrity must be defended against all threats. Hamlet is one such threat.

At the same time, Ophelia is deeply romantic, and feels genuine love for Hamlet. She is torn in two by the dictates of filial piety and reasons of the heart. A naive, unstable creature, Ophelia lacks the maturity and strength of character to be able to reconcile these two conflicting imperatives. She has found herself caught between the social demands of the medieval world with its insistence on a woman's purity and the developing Renaissance concept of romantic love as expressed in countless poems and songs. Her father is dead, and the man who killed him has rejected her; she is effectively all alone in a hostile world. Not surprisingly, Ophelia rapidly descends into insanity.

In Act IV, Scene 5, Ophelia behaves erratically, talking incoherently and singing songs of unrequited love. Unlike the case of Hamlet we are utterly convinced of Ophelia's madness. She is simply too innocent and too naive to engage in the kind of sly subterfuge of her erstwhile lover. Yet still she is rejected, this time by Gertrude, and her subsequent tragic end has a terrifying sense of inevitability about it.

While it is difficult to determine exactly what causes Ophelia to go mad, there are several contributing factors that may have some connection to her madness.

Ophelia is a generally weak character; she bends to the will of everyone: the king and queen, her brother, her father, and Hamlet. When these people are removed from her, or disapprove of her, she breaks.

When Hamlet mistakenly kills Polonius later in Act III, Ophelia goes mad. Her madness may well be a result of a combination of factors:

1. She loves Hamlet and is not only shunned by him, but treated horribly by him. 2. Her father, whom she also loves, is dead. 3. Her father has been murdered by the man she wants to marry. 4. She is alone in the world now that Leartes is away, her father is dead, and Hamlet has completely rejected her. 5. She may be pregnant. (This possibility is indicated in Act IV Scene 6 when she sings about a maid losing her virginity and later in the same scene when she gives herself rue--which could be used to cause a miscarriage.)

Also, rue, when used incorrectly as an abortifacient, may cause irratic behavior, or "madness"

Check out Enotes page on Hamlet for more information.

There is an interesting web site that analyzes the meanings behind the different flowers Ophelia presents to people during her second mad scene...

Why has Ophelia gone mad?