ng in my face,
Have pluck'd my nipple from his boneless gums,
And dash'd the brains out, had I so sworn as you
Have done to this.

Here Lady Macbeth asserts (1) that Macbeth proposed the murder to her:
(2) that he did so at a time when there was no opportunity to attack
Duncan, no 'adherence' of 'time' and 'place': (3) that he declared he
wou'd _make_ an opportunity, and swore to carry out the murder.

Now it is possible that Macbeth's 'swearing' might have occurred in an
interview off the stage between scenes v. and vi., or scenes vi. and
vii.; and, if in that interview Lady Macbeth had with difficulty worked
her husband up to a resolution, her irritation at his relapse, in sc.
vii., would be very natural. But, as for Macbeth's first proposal of
murder, it certainly does not occur in our play, nor could it possibly
occur in any interview off the stage; for when Macbeth and his wife
first meet, 'time' and 'place' _do_ adhere; 'they have made themselves.'
The conclusion would seem to be, either that the proposal of the murder,
and probably the oath, occurred in a scene at the very beginning of the
play, which scene has been lost or cut out; or else that Macbeth
proposed, and swore to execute, the murder at some time prior to the
action of the play.[291] The first of these hypotheses is most
improbable, and we seem driven to adopt the second, unless we consent to
burden Shakespeare with a careless mistake in a very critical passage.

And, apart from unwillingness to do this, we can find a good deal to say
in favour of the idea of a plan formed at a past time. It would explain
Macbeth's start of fear at the prophecy of the kingdom. It would explain
why Lady Macbeth, on receiving his letter, immediately resolves on
action; and why, on their meeting, each knows that murder is in the mind
of the other. And it is in harmony with her remarks on his probable
shrinking from the act, to which, _ex hypothesi_, she had already
thought it necessary to make him pledge himself by an oath.

Yet I find it very difficult to believe in this interpretation. It is
not merely that the interest of Macbeth's struggle with himself and with
his wife would be seriously diminished if we felt he had been through
all this before. I think this would be so; but there are two more
important objections. In the first place the violent agitation described
in the words,

If good, why do I yield to that