Originally Posted by Regit
The ghost, like all other characters, is subject to characterisation. Meaning, again, that its course of action is determined by its person and purposes. Its ghostly nature does give it different physical abilities and activities, yet changes nothing of its mental existence. Therefore, the dead King does not know exactly how Hamlet recieves his death. Whilst the rest of the royal family recover quickly and their grief is clearly but "the strappings and suits of woes" and forget underneath, it is perhaps natural for the ghost to doubt others' devotion to it, including Hamlet's. For, though Hamlet's grief is and does not seem, he does have on him, as the rest of them have, the similar "customary suits of solemn black", the "windy suspiration of forc'd breath", the "fruitful river in the eye", and the "dejected havious of the visage," identical to an outside eye; and it is a difficult task to separate him, who is with real grief from those without. Yet...
"He could have appeared in Hamlet's bedroom to Hamlet alone," you say?
"Why, what should be the fear?
I do not set my life at a pin's fee;
And for my soul, what can it do to that,
Being a thing immortal as itself:
It waves me forth again; I'll follow it."
The enthusiasm of Hamlet to follow Horatio to see the ghost that might be his father's spirit is a testiment to his devotion (his soul and, thus, his purpose is as immortal as the ghost). It also proves Hamlet's bravery and determination, brought about only by his faithful interpretation of the ghost's appearance. For if his doubt that it might be a spirit of "goblin damn'd", or had "wicked" intents is more than his yearning to know what the spirit of his father has to say and to have justice, he would not have come, and he would not have followed it. YET, after all proofs, the ghost still has to be further reassured:
"list, Hamlet, oh list.
If thou didst ever thy dear father love."
The ghost's goal is decidedly revenge. Therefore, one aspect of the ghost's purpose is to find its ally; and it must embark upon this with care. It could have also appeared in Gertrude's room; her duty to avenge it is as heavy as Hamlet's if not more. It could also have appeared and spoken anywhere, for it is also a people's duty to avenge its King. Yet, trust is not a murdered, betrayed, and forgoten soul's quality.