What is the significance of Macbeth's soliloquy before the death of Banquo (3.1. 48-72)?a. Does it reveal the setting? b. Does it...

Macbeth's soliloquy of Act III, Scene 1 propels the theme
of "vaulting ambition" to its fears and guilts.  As Shakespeare's soliloquies always
reveal the inner thoughts of his characters, Macbeth's soliloquy indicates his paranoia
and guilt. For, now that he is king, he worries that he has killed Duncan for nought
since the witches have foretold that Banquo's sons will be kings.  Macbeth agonizes
about how to be rid of Banquo who is very cautious:

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He hath a wisdom that doth guide his valor

To act in safety. There is none but he
Whose being I do fear; and
under him
My genius is rebuke, as it is said(60)
Mark Antony's was
by Caesar.

Macbeth also feels
some jealousy of Banquo:

For
Banquo's issue have

I filed my
mind.

since he is childless: 
"Upon my head they placed a fruitless crown."

Above all,
Macbeth's "vaulting ambition" which has led him to paranoia, now has finally brought him
guilt and misery

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For them the gracious Duncan have I
murdered,(70)
Put rancors in the vessel of my peace
Only for them,
and mine eternal jewel
Given to the common enemy of man,
To make
them kings, the seed of Banquo
kings! 

Nevertheless,
after Macbeth mulls over his fears and guilts, his "vaulting ambition" overcomes the
other emotions because he orders the murderers to kill not only Banquo, but his son
Fleance, as well.