Shakespeare did not feel himself free to depart widely from his original. The four speeches of the ghost beneath the stage, resulting in Hamlet's removal from one side of the stage to the other, have their counterpart in Fratricide Punished (Furness ii. 125-126), and hence, in the opinion of some, were a feature of the pre-Shakespearean version. The issue of secrecy is never again raised. Marcellus is no more heard of, and Horatio is the most loyal of confidants. The first oath, "In faith, my lord, not I," was really sufficient. We can, however, see a reason why the ghost should approve of Hamlet's swearing his friends to secrecy: this indicates Hamlet's purpose of undertaking the revenge himself and of carrying it out with his own hand.
But with these minor exceptions, occasioned by the dramatic form and by the established tradition among playgoers, we may look to the words and actions of the ghost as our sole infallible guide in interpreting the play. What indications do these afford?
The ghost's command to Hamlet is threefold (Ransome, Shakespeare's Plots, p. 12):
If thou didst ever thy dear father love—
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Revenge his foul and most unnatural murder.
But howsoever thou pursuest this act,
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Taint not thy mind, nor let thy soul contrive
Against thy mother aught.
