Immediately before Macbeth enters Duncan's chamber to kill the king,
Lady Macbeth speaks from outside the chamber seems to be getting a
little nervous about the deed. She speaks the first line of the scene
by saying, "That which hath made them drunk hath made me bold" (II,II,
1-2). In this line the Lady is telling the audience that through
drinking the same wine as her visitors, and now her victims, she has
become emboldened. This is understandable through a very literal
translation by saying that since the victims are drunk, and thus in a
drunken sleep, it will be easier for her and her husband to carry out
their plan. From a completely other angle, it could be seen that what
has made Lady Macbeth bolder was information, in the form of the
prophecy by the witches. So conceivably, Duncan and his entourage are
"drunk" on information, thus letting their guard down and making them
vulnerable. Meanwhile, the Lady uses information to spark her plan,
which she likely never thought of before the witches had made their
prophecy. I think Shakespeare could have intended to have either of
these interpretations understood by the audience. Regardless, however,
the boldness, as it often does with "super-villians", becomes their
downfall. When used incorrectly, confidence often times is the fast
track to demise.