Why Hamlet calls his father's ghost "boy"?

At the beginning of the play, sentinels and Horatio witness the appearance of old King Hamlet’s ghost, and report to young Hamlet, who decides to check that himself.

The ghost meets Hamlet, tells how he was murdered by Claudius, and asks for Hamlet’s body. Old King Hamlet’s ghost then possesses his son’s body. From this point afterwards, Hamlet talks with seemingly mad words, until the ghost leaves Hamlet’s body when Hamlet apologizes to Laertes and asks for a fair fencing match.

Switching of souls are performed three times in this scene to affirm this design. The moment who owns the body can be identified by how one calls the other.

Dialogue

Ghost. [Act 1, Scene 5]

Fare thee well at once;

The Glow-worm shows the Matin to be near,

And gins to pale his uneffectual Fire:

Adieu, adieu, Hamlet: remember me. [Exit.]

Hamlet. [Young]

Oh, all you host of Heaven! Oh, Earth; what else?

And shall I couple Hell? Oh, fie: hold my heart;

And you my sinews, grow not instant Old;

But bear me stiffly up: Remember thee?

Ay, thou poor Ghost, while memory holds a seat

In this distracted Globe: Remember thee?

Yea, from the Table of my Memory,

I’ll wipe away all trivial fond Records,

All saws of Books, all forms, all pressures past,

That youth and observation copied there;

And thy Commandment all alone shall live

Within the Book and Volume of my Brain,

Unmixed with baser matter; yes, yes, by Heaven:

Oh, most pernicious woman!

Oh, Villain, Villain, smiling damned Villain!

My Tables, my Tables; meet it is I set it down,

That one may smile, and smile and be a Villain;

At least I’m sure it may be so in Denmark;

So, Uncle there you are: now to my word;

It is; Adieu, Adieu, Remember me: I have sworn it.

The First Switch

[Enter Horatio and Marcellus.]

Hamlet. [Old]

Never make known what you have seen tonight.

Both.

My Lord, we will not.

Hamlet. [Old]

Nay, but swear it.

Horatio.

Infaith my Lord, not I.

Marcellus.

Nor I, my Lord: in faith.

Hamlet. [Old]

Upon my sword.

Marcellus.

We have sworn my Lord, already.

Hamlet. [Old]

Indeed, upon my sword, Indeed.

Ghost. [Young Hamlet from off the stage]

Swear.

Hamlet. [Old]

Ah ha, boy, say’st thou so. Art thou there truepenny?

[To Horatio and Marcellus]

Come on, you hear this fellow in the cellarage:

Consent to swear.

Horatio.

Propose the Oath, my Lord.

Hamlet. [Old]

Never to speak of this that you have seen.

Swear by my sword.

Ghost. [Young Hamlet from off the stage]

Swear.

The Second Switch

Hamlet. [Old]

Hic and ubique? Then we’ll shift for ground,

Come hither Gentlemen,

And lay your hands again upon my sword,

Never to speak of this that you have heard:

Swear by my Sword.

Ghost. [Old Hamlet from off the stage]

Swear.

The Third Switch

Hamlet. [Young]

Well said, old Mole, can’st work in the ground so fast?

A worthy Pioneer, once more remove, good friends.

Horatio.

Oh, day and night; but this is wondrous strange.

Hamlet. [Old]

And therefore as a stranger give it welcome.

There are more things in Heaven and Earth, Horatio,

Than are dreamed of in our Philosophy. But come,

Here as before, never so help you mercy,

How strange or odd soever I bear myself;

Notes

*remember me: a commandment from young Hamlet’s father. The ghost leaves the stage after this line. “Remember me” will appear again after two times “Remember thee.” The repetition can be a hint to treat remember as a wordplay of re-member, to let the ghost be a member of the living again. Next paragraph shows how young Hamlet hesitates to let his father’s spirit occupy his body.

*what else?: What else will happen after the ghost taking young Hamlet’s body is answered in following lines.

*shall I couple Hell?: Couple has the usage of to associate or link together. Young Hamlet questions himself whether he should associate himself with the hell (“couple Hell”) by switching souls with his father or not.

*my sinews, grow not instant Old: Young Hamlet imagines and worries that his body will be instantly old when his father’s ghost takes over his body.

*bear me stiffly up: Young Hamlet imagines the ghost will control his body stiffly like a zombie or walking dead.

*Remember thee?: a question whether to accept the ghost’s commandment of “re-member me” to switch souls or not. The answer seals in “Remember me” at the end on his monologue.

*while memory holds a seat in this distracted Globe: Distract has the usage of to divert or switch; globe of earth or world. The “distracted Globe” is a hint to switch between the world above and below the ground. To remember is to bring back “memory” that holds a seat in the word’s definition, a hint to distract the word remember to re-member.

*remember thee?: The repetition of “remember thee” is an alert to notice the difference of “me” and “thee” in this paragraph.

*from the Table of my Memory, I’ll wipe away all trivial fond Records . . . That youth and observation copied there: Before the ghost taking over the body, young Hamlet wants to erase all his trivial records “that youth and observation copied” from the table of his memory. He will “set down” these records in his table-books (“My Tables, my Tables”) so that he can recover these records after he regains his body.

*And thy Commandment all alone shall live . . . Unmixed with baser matter: Young Hamlet will keep only the ghost’s commandment, not to mix with baser matter in his memory while the ghost possessing his body.

*My Tables, my Tables; meet it is I set it down: Hamlet writes down what will be erased from him memory into his table-books. Meet has the usage of fit or appropriate. “Meet it is” can mean it is proper to do something, such as “and it is meet I presently set forth” (The Merchant of Venice), or “that it is meet so few should fetch the Prince” (Richard III).

*So, Uncle there you are: now to my word: “Uncle there you are” says young Hamlet’s uncle Claudius is one may smile and be a Villain in Denmark. This is the last line from young Hamlet in this paragraph. Old King Hamlet would not call Claudius uncle. After this line the ghost will possess Hamlet’s body. The “now to my word” is the first line of the ghost in Hamlet’s body.

Who is possessing the body can be known by the content only, not the speaker’s name; e.g. old King Hamlet would call young Hamlet “boy,” not the reverse.

*Adieu, Adieu, Remember me: I have sworn it: No quotation mark exists in the 1623 folio. The ghost is possessing Hamlet’s body now, and gives his commandment “Adieu, Adieu, Remember me” the second time to young Hamlet, corresponding to the ghost’s first commandment “Adieu, adieu, Hamlet: remember me” that he has sworn before, to become a member of the living again. After this line Hamlet will act and talk as if he is mad.

*Ah ha, boy, say’st thou so: Old King Hamlet owns the body now and calls young Hamlet in the underground “boy.”

*Art thou there truepenny?: Truepenny says young Hamlet is a trustful person. This question suggests that old King Hamlet wonders if the soul of a living man can really be in the underground.

*this fellow in the cellarage: It’s less likely young Hamlet would call his father “fellow” or “boy.”

*Hic and ubique? Then we’ll shift for ground: Hic and ubique, here and everywhere, is a hint that the soul of old and young Hamlet can be anywhere in this play. The speaker here is old Hamlet, who asks young Hamlet to “shift” souls. After this line the speaker will be young Hamlet.

*old Mole: The calling of “old Mole” suggests that the speaker now is young Hamlet. Mole has the usage of one who lives or works in the darkness.

*once more remove: They switch again. Old Hamlet occupies the body after this line. Both “shift” and “remove” suggest the point of soul-switching.

*day and night; but this is wondrous strange: This line compares the switching of day and night with the soul-switching of the living and the dead.

*therefore as a stranger give it welcome: Old King Hamlet is like a stranger to the living world after possessing his son’s body.

*more things in Heaven and Earth, Horatio, than are dreamed of in our Philosophy: Heaven and earth may allude to the dead and the living. A body possessed by ghost is beyond rules of philosophy. The word philosophy appears twice in this play. The other is a question why people will pay “an hundred Ducats a piece” for Claudius’ little picture, which is “more than Natural.”

Hamlet. [Act 2, Scene 2]

It is not strange: for mine Uncle is King of Denmark, and those that would make mows at him while my Father lived; give twenty, forty, an hundred Ducats a piece, for his picture in Little. There is something in this more than Natural, if Philosophy could find it out.

This more than natural issue indicates the witchcraft of Eden serpent owned by the wizard Claudius, who can influence people to give high price for his little (nasty, inferior) picture.

*How strange or odd soever I bear myself: Old King Hamlet (“I”) who bears his soul on young Hamlet’s body would feel “strange or odd.” A normal person will not have such feeling.

Hamlet’s Transformation

Various odd lines in this play can be better reasoned by the assumption of ghost possessing, such as the description of Hamlet’s transformation:

Claudius. [Act 2, Scene 2]

Something have you heard

Of Hamlet’s transformation: so I call it,

Since not the exterior, nor the inward man

Resembles that it was. What it should be

More than his Father’s death, that thus hath put him

So much from the understanding of himself,

I cannot deem of.

Other lines like “Hamlet from himself be taken away,” Laertes’s “The devil take thy soul,” and Hamlet’s “something in me dangerous.”