Initially, Horatio is skeptical:
* In Act I, Scene II, Horatio expresses doubt about Hamlet's sanity. He sees Hamlet's melancholy and believes it's due to the recent death of his father. He states, "He seems to have lost all his mirth. For I have seen him in the court of Denmark, and he has looked like the innocent flower, but most foul."
* Horatio even attempts to reason with Hamlet, believing his grief is excessive.
However, Horatio becomes increasingly convinced of Hamlet's madness:
* As the play progresses, Horatio witnesses Hamlet's erratic behavior, including his strange interactions with Ophelia, his soliloquies, and his violent actions.
* Horatio observes Hamlet's "antic disposition," which is a calculated pretense of madness. He realizes that Hamlet is not simply grieving but deliberately feigning madness to achieve his own ends.
Horatio ultimately understands Hamlet's true motives:
* By the end of the play, Horatio fully comprehends Hamlet's feigned madness and his plot for revenge. He acts as Hamlet's confidant, aiding him in his plan and even witnessing the final confrontation with Claudius.
Therefore, Horatio's perception of Hamlet's madness changes throughout the play. Initially skeptical, he eventually comes to understand Hamlet's deliberate pretense, recognizing the strategic use of madness to achieve his revenge.