In act 3, scene 1, Hamlet resolves to keep his promise of revenge. He has formulated a plan to use “players” (or actors) to reenact the murder of his father before his uncle Claudius and his mother. In watching their reactions, he hopes to discover if his father’s ghost was telling the truth about being poisoned. Hamlet wants to be absolutely certain that Claudius is guilty, because if it is true, then he feels he must kill Claudius, as he told his father's ghost he would.
Briefly, in act 3, scene 1, Hamlet considers not keeping his promise to his father’s ghost. In his most famous soliloquy, he briefly considers whether or not to commit suicide instead. Killing Claudius would be a risky feat, given that Claudius is king, and Hamlet knows it would be seen as a traitorous act. Probably, most everyone would disbelieve his “ghost” story and assume he did not want Claudius to marry his mother. Or they would assume Hamlet was jealous for the throne.
Not only does Hamlet know killing Claudius is risky in a life-threatening regard, but he also knows it will burn bridges between him and his mother for good. His mother seems to love Claudius, having married him just a month after the loss of her first husband. If he kills Claudius, his mother will grieve. Even though Hamlet is angry at his mother, some part of him longs for restoration with her. In Elizabethan times, marrying a family member was known to be a great sin, which is why Hamlet is disgusted with his mother for marrying Claudius.
Furthermore, Hamlet may feel that murdering the king would separate him from pure, godly Ophelia, whether in a practical sense (if he is caught) or in a spiritual sense (because she is a saintly sort). This may be why he decides to push her away later in this act.
Hamlet sees himself as stuck in a lose-lose situation, which is the reason for his suicide contemplation:
To be, or not to be: that is the question:
Whether tis nobler in the mind to suffer
The slings and arrows of outrageous fortune,
or to take arms against a sea of troubles,
and by opposing end them? To die: To sleep.
Here, Hamlet contemplates if it would be “nobler” to face his future head-on, taking revenge on Claudius and suffering all the figurative “slings and arrows” that he expects to be thrown his way for doing so. He also contemplates whether suffering his fate would be better than opposing fate itself by killing himself so that he does not fulfill his evil promise.
Hamlet resolves not to kill himself, because he fears what comes after death. He reasons,
But that the dread of something after death,
The undiscover’d country from whose bourn
No traveller returns, puzzles the will
And makes us rather bear those ills we have
Than fly to others that we know not of?
Thus conscience does make cowards of us all . . .
Preceding this excerpt, Hamlet has just taken some time to list the various oppressions a person might avoid by being dead. But here, he exposes that he fears that the afterlife might be worse than reality. He describes death as “an undiscovered country / from whose bourn no traveler returns.” This is compounded by the fact that Elizabethans considered suicide to be a sin that would send you directly to hell in the afterlife.
Another possible anxiety in this speech is that Hamlet fears breaking his oath to his ghost father would lead to separation from him in the afterlife. Thus, Hamlet concludes that his “conscience” has made a coward of him.
The twofold resolution of Hamlet, to remain living and pursue the path of revenge, is a decision that seals his fate. The soliloquy shows just how unhealthy his state of mind is at this point in the play. Seeing his father’s ghost, realizing his uncle’s betrayal, and losing respect for his mother have taken a toll on his mental health and thrown him into a state of depression. To live, for Hamlet, is “to grunt and sweat under a weary life.” He sees every aspect of the future pessimistically, like a burden. He fails to see that suicide is never a good option. Furthermore, Hamlet is thinking with an “either/or” mentality. He does not consider any other hopeful alternatives, such as exposing Claudius, trapping him into a confession, talking to his mother or crafty Polonius (or seeking support from a myriad of other brave young soldiers faithful to him). Ultimately, his lose/lose situation is a concoction of an unhealthy mind.
One final note is that in Shakespeare’s plays, supernatural entities often appear to mess with the fates of kings. For example, the witches in Macbeth give Macbeth a prophecy with the singular purpose of causing his downfall. In Othello, his mother (a kind of witch doctor) indirectly causes Othello’s downfall by tying his happiness in love to an enchanted handkerchief she passes down to him. Many in Elizabethan times understood ghosts to be demons, evil entities that could take different forms in order to deceive and mislead the human beings they encountered. It is a possibility that the rashly made promise was not the request of Hamlet’s real father, but a demonic being intending to cast him into turmoil and bring about his destruction.