In the opening scene of Hamlet, what is Horatio's attitude towards the ghost before it appears and after he sees it?
At first, Horatio refuses to believe in the reality of the ghost. Marcellus, who has seen the ghost, says:
Horatio says ’tis but our fantasyAnd will not let belief take hold of him
If thou art privy to thy country’s fate,Which happily foreknowing may avoid,Oh, speak!
At first mention of the ghost, Horatio is not a believer. He says:
Tush, tush, 'twill not appear.
As the ghost appears, Horatio claims:
It harrows me with fear and wonder.
So while it is right in front of him, his curiosity grows and his senses appropriately tell him he is indeed looking at a ghost.
As the ghost leaves, Horatio admits that he would not have believed this unless he saw it with his own two eyes:
Before my God, I might not this believe
Without the sensible and true avouch
Of mine own eyes.
Horatio's attitude has to do with a belief in the afterlife. He was known as a scholar and would have likely been a skeptic. The above quotes demonstrate this skeptical attitude in him consistently.