How is Horatio different from the others in Hamlet? Why is he skeptical?Act One, Scene 1 of "Hamlet"

In Shakespeare's "Hamlet," Horatio, the close friend who is willing to die beside Hamlet is extremely astute and referred to as "the scholar."  He is originally skeptical of the ghost because he believes it to be a "fantasy" (I,i,23).  So, the others beg him to accompany them on their watch that he may see the apparition and judge.  When Horatio sees the ghost, he agrees that it resembles King Hamlet, and he tells the others that he is filled with "fear and wonder" (I,i,54). Nevertheless, Horatio is braver than the others and addresses the ghost, but it refuses to respond.  Horatio tells the others that he might not have believed in this spectre had he not seen it himself.  Also, he notices that this ghost is clothed in armor resembling that which he wore when he defeated Fortinbras of Norway. Because of this, Horatio fears that young Fortinbras will challenge Denmark, entering the country in battle; he fears a strange eruption in the state:

In what particular thought to work I know not;/But in the gross and scope of my opinion,/This bodes some strange eruption to our state.

In this exposition to Shakespeare's "Hamlet," Horatio is clearly established as a strong friend to Hamlet as the others have him see the ghost so that he will call Hamlet to its witness. Horatio is also intuitive as he has a sense of foreboding.