In Hamlet, why does Hamlet hesitate to carry out the commands of the ghost?

Hamlet's hesitation to act is rooted in two different
aspects of the drama: Shakespeare's development of Hamlet's very complex character and
the conventions of the revenge play, a popular dramatic genre of the
time.

In the revenge play, and Hamlet
is a revenge play, the plot develops in certain steps. Before the closest blood relative
can take revenge for the murder of a loved one, the murder must first be established and
the guilty perpetrator identified. These two steps take quite some time
in Hamlet, as the young prince must convince himself that the ghost
he has seen is not a false vision (an instrument of evil), that his father had indeed
been murdered, and that Claudius is indeed guilty of the crime. Hamlet goes to great
effort--feigning madness, arranging the play at court, and enlisting Horatio's aid--to
make sure that Claudius murdered Old Hamlet. Both Hamlet's and Claudius' elaborate
secret plotting, which makes up most of the play, are consistent with the conventions of
the revenge play. In other words, if Hamlet had met the ghost and then immediately
exacted revenge, there would be no play!

Hamlet's
hesitation, however, has been interpreted most often in terms of his own complicated
character and his position in Denmark. Denmark is weakened and threatened by foreign
invaders, the court is in disarray, and killing a king under any circumstances is a
serious matter. To revenge his father, Hamlet must commit regicide, the most serious
crime in his society. He hesitates in the face of these
circumstances.

Hamlet is also a deeply spiritual person, a
student of theology who had been called home from his studies when his father died. The
act of murder is a mortal sin. He is trapped between his own moral beliefs and his
responsibility to avenge his father's murder. Deeply conflicted, he considers suicide,
but self-murder is a sin, as well. Hamlet finds himself in the wrong place at the wrong
time, trapped by his circumstances and his own
identity.

Finally, Hamlet is deeply depressed. A serious,
introspective, philosophical person by nature, his father's death and his mother's
marriage to Claudius--an immoral, incestuous act and one of betrayal of Hamlet's
father--plunge Hamlet into a state of deep depression. His separation from Ophelia and
her subsequent death make his depression even more profound. He becomes obsessed with
death and the futility of life. He examines his own character again and again. He is
paralyzed, incapable of action throughout most of the
drama.

For all of these reasons, Hamlet does not act
quickly to exact revenge after meeting the ghost on the
battlements.