Hamlet and Horatio are friends and schoolmates. A key to Horatio's pragmatic, level-headed character comes early in the play, as together the two encounter the ghost of Hamlet's father. Hamlet says the following to Horatio:
There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.
By "philosophy," Hamlet means Horatio's rational method of thinking, a rationality that excludes the supernatural—at least until Horatio witnesses it. So we know from the start that Horatio is a rational person.
Horatio is also loyal to Hamlet's demand that he never reveal he knows about the ghost and that he never betray Hamlet when Hamlet acts the madman:
Here, as before, never, so help you mercy,
How strange or odd soe'er I bear myself
(As I perchance hereafter shall think meet
To put an antic disposition on),
That you, at such times seeing me, never shall—
With arms encumbered thus, or this headshake,
Or by pronouncing of some doubtful phrase,
As “Well, well, we know,” or “We could an if we would,”
Or “If we list to speak,” or “There be an if they might,”
Or such ambiguous giving out—to note
That you know aught of me.
Hamlet is actually much like Horatio in his empiricism, the desire to confirm truth through experimentation rather than to accept it on faith. Although deeply anguished at the Ghost's words, Hamlet rationally goes about confirming what the Ghost has said is true before moving against Claudius
. We can imagine Horatio doing the same. Unlike the hot-headed Laertes
, Horatio, like Hamlet, tends to be cautious.
In contrast to his friend, however, Horatio does not suffer the same torments as Hamlet, though, of course, he does not have to deal with his uncle having murdered his father and married his mother.
Throughout the play, amid a corrupt court, Horatio will stay true to Hamlet, and Hamlet can trust him at the end to tell the story of what happened both accurately and sympathetically.