When he first sees the ghost, Horatio and Marcellus try to restrain him, Horatio saying: .
What if it tempt you toward the flood, my lord,.
Or to the dreadful summit of the cliff.
That beetles o'er his base into the sea,.
And there assume some other horrible form,.
Which might deprive your sovereignty of reason,.
And draw you into madness? (1.4.72-77).
Horatio is afraid that the ghost will get Hamlet to follow him to a cliff hanging over the sea, and then change into some other apparition, making Hamlet lose his mind and his sovereign power of reason. These words are very ironic, for as a result of seeing the ghost and hearing the dreadful truth about his father's murder and mother's adultery Hamlet says he will put on an "antic disposition," telling the others that he will act oddly, but that they mustn't tell anyone why he is doing so. Hamlet has already told us that he is a man of thought rather than action (earlier in the play he says that Claudius is as different to his father "as I to Hercules"), and he is going to act oddly so that the King doesn't suspect Hamlet is plotting his downfall. However, Horatio and Marcellus even now think that Hamlet is acting rather strangely, saying, "These are wild and whirling words, my lord", and "this is wondrous strange.".
The next passage of interest is in Act II Sc II, when Claudius says to Rozencrantz and Guildenstern:.
Something have you heard.
Of Hamlet's transformation; so call it,.
Since nor th' exterior nor the inward man.
Resembles that it was. (2.2.4-7).
Claudius is keen to talk of Hamlet's rumored madness, because he thinks Hamlet might know something about his treachery and wants to deflect his guilt and detract from Hamlet's credibility. To the audience, who have already heard the ghost's speech, Claudius seems to be going over the top, saying that he can't imagine what has rendered Hamlet mad and going back to childhood memories.
