This interpretation still seems to me not unnatural.  The alternative (unless we adopt the idea of an agreement prior to the action of the play) is to suppose that Lady Macbeth refers throughout the passage to some interview subsequent to her husband’s return, and that, in making her do so, Shakespeare simply forgot her speeches on welcoming Macbeth home, and also forgot that at any such interview ‘time’ and ‘place’ did ‘adhere.’  It is easy to understand such forgetfulness in a spectator and even in a reader; but it is less easy to imagine it in a poet whose conception of the two characters throughout these scenes was evidently so burningly vivid.

FOOTNOTES: 

[Footnote 291:  The ‘swearing’ might of course, on this view, occur off the stage within the play; but there is no occasion to suppose this if we are obliged to put the proposal outside the play.]

[Footnote 292:  To this it might be answered that the effect of the prediction was to make him feel, ’Then I shall succeed if I carry out the plan of murder,’ and so make him yield to the idea over again.  To which I can only reply, anticipating the next argument, ’How is it that Shakespeare wrote the speech in such a way that practically everybody supposes the idea of murder to be occurring to Macbeth for the first time?’]

[Footnote 293:  It might be answered here again that the actor, instructed by Shakespeare, could act the start of fear so as to convey quite clearly the idea of definite guilt.  And this is true; but we ought to do our best to interpret the text before we have recourse to this kind of suggestion.]

NOTE DD.

DID LADY MACBETH REALLY FAINT?

In the scene of confusion where the murder of Duncan is discovered, Macbeth and Lennox return from the royal chamber; Lennox describes the grooms who, as it seemed, had done the deed: 

Their hands and faces were all badged with blood;
So were their daggers, which unwiped we found
Upon their pillows: 
They stared, and were distracted; no man’s life
Was to be trusted with them.

Macb. O, yet I do repent me of my fury
That I did kill them.

Macd. Wherefore did you so?

Macb. Who can be wise, amazed, temperate and furious,
Loyal and neutral, in a moment?  No man: 
The expedition of my violent love
Outrun the pauser, reason.  Here lay Duncan,
His silver skin laced with his golden blood;
And his gash’d stabs look’d like a breach in nature
For ruin’s wasteful entrance:  there, the murderers,
Steep’d in the colours of their trade, their daggers
Unmannerly breech’d with gore:  who could refrain,
That had a heart to love, and in that heart
Courage to make’s love known?