I need three important points for my thesis how the witches influenced Macbeth to kill Duncan in Macbeth.

How Shakespeare reveals his
characters:

1.What characters say to each
other

2.What characters say about other
characters

3.What characters say to
themselves

4.What characters do
(actions).

Notice, that the Witches are only
revealed through language. Only #1-3 apply, not #4.  They do not do
anything.  Their actions are non-invasive.  They exist on the periphery of society,
commenting on it rather than participating in it.

As
such, Language is Power: “The pen is mightier than the
sword.”  He who controls language, controls others.
Language (argument) is used to attain and maintain position by royalty, between nations,
by clergy in the church.

Macbeth is won over
by language from women:

•The
Witches  provide Macbeth the nouns:

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“All hail,
Macbeth,

Thane of
Glamis,

Thane of Cawdor,

That
shalt be King
hereafter.”

(I.iii.50-53)

•Lady
Macbeth provides Macbeth the verbs:

•“Look
like the time.” •“Bear welcome…” •“Look like the innocent flower, but be the serpent
under’t.” •“Leave all the rest to me.”
(I.v.66-76)

Specifically, the Witches use the
language of Equivocation: •Shakespeare often uses intentionally vague
language for ambiguity, double meaning, and to spare
syllables.

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"Something wicked this way comes."
(IV.i.)

•They use the
language of confusion; ambiguity; double meanings; half-truths; paradoxes;
riddles

•“Foul is fair and fair is
foul”

•“nothing is but what is
not”

•“Lesser than Macbeth and
greater.”

•They use Equivocal Morality to appeal
to Macbeth's heightened sense of ambition as a male:

How do
you know what’s good, or who’s good, if there’s overlap between good and evil ("foul is
fair")?

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•“These solicitings cannot be evil, cannot be
good…”

In the end, the
witches are like the oracles of Ancient Greek tragedies.  They are like the Riddle of
the Sphinx.  Even when the male thinks he has answered their equivocations correctly, he
will later learn that there was a duality or paradoxical "other" side to the riddle
which he originally forgot.  This other side is indicative of the female: males think
like males, not like females.  In this way, the witches punish Macbeth for thinking like
a typical arrogant male.