Banquo is murdered, but still Macbeth cries:
“I am cabined, cribbed, confined, bound in
To saucy doubts and fears.”
The scene with the ghost of Banquo follows, where-in Macbeth again shows
the nervous imaginative Hamlet nature. His next speech is mere
reflection, and again Hamlet might have framed it:
“the time has been
That when the brains were out the man would die
And there an end”: ...
But while fear may be an adequate motive for Banquo's murder, it can hardly explain the murder of Macduff's wife and children. Shakespeare feels this, too, and therefore finds other reasons natural enough; but the first of these reasons, “his own good,” is not especially characteristic of Macbeth, and the second, while perhaps characteristic, is absurdly inadequate: men don't murder out of tediousness:
“For mine own good
All causes shall give way: I am in blood{1}
Stepped in so far, that, should I wade no more,
Returning were as tedious as go o'er.”
{Footnote 1: It seems to me probable that Shakespeare, unable to find an adequate motive for murder, borrowed this one from “Richard III.” Richard says:
“But I am in
So far in blood that sin will pluck on sin”—
This is an explanation following the fact rather than a cause producing it—an explanation, moreover, which may be true in the case of a fiendlike Richard, but is not true of a Macbeth.}
Take it all in all, this latter reason is as poor a motive for cold-blooded murder as was ever given, and Shakespeare again feels this, for he brings in the witches once more to predict safety to Macbeth and adjure him to be “bloody, bold and resolute.” When they have thus screwed his courage to the sticking place as his wife did before, Macbeth resolves on Macduff's murder, but he immediately recurs to the old explanation; he does not do it for his “own good” nor because “returning is tedious “; he does it
“That I may tell pale-hearted fear it lies,
And sleep in spite of thunder.”
It is fair to say that Shakespeare's Macbeth is so gentle-kind, that he can find no motive in himself for murder, save fear. The words Shakespeare puts into Hubert's mouth in “King John” are really his own confession: