Who is Horatio, and what purpose(s) does he serve in Hamlet?How does Horatio's nature compare to that of Hamlet's?
Horatio is Hamlet's best friend. More than that, Horatio, although much lower in rank around the castle, is someone Hamlet admires. For unlike Hamlet, who is rather split, Horatio is measured. Where Hamlet is overly sensitive, rash and given to the deepest of thoughts, Horatio is well balanced. Here, in his own words, is Hamlet's praise of his dear friend (Act 3, Scene 2):
For thou hast been
As one, in suff'ring all, that suffers nothing;
A man that Fortune's buffets and rewards
Hast ta'en with equal thanks; and blest are those
Whose blood and judgment are so well commeddled
That they are not a pipe for Fortune's finger
To sound what stop she please. Give me that man
That is not passion's slave, and I will wear him
In my heart's core, ay, in my heart of heart,
As I do thee.
And because Hamlet has such esteem for Horatio, he trusts him and confides in him. Thus Horatio knows about the Ghost and Claudius and the murder and the plot involving Rosencrantz and Guildenstern. And it is with Horatio that Hamlet plans to meet in the graveyard on Hamlet's return to Elsinore.
Horatio is Hamlet's confidant, so he knows Hamlet's whole tragic story. And it is for this reason that Hamlet tells Horatio to relate his story to the world when Hamlet is no longer there. In the last scene, Hamlet tells Horatio:
...Horatio, I am dead;
Thou livest; report me and my cause aright
To the unsatisfied.
...If thou didst ever hold me in thy heart,
Absent thee from felicity awhile,
And in this harsh world draw thy breath in pain,
To tell my story.
And Horatio, who has been by his friend's side from the first act to the last, will obey the Prince.