What are some quotes in Macbeth which support the idea that Macbeth has free will?
Although Macbeth is encouraged to kill king Duncan when he hears about the witches' prophecy and when Lady Macbeth verbally pressures him to do that, Macbeth, alone, is responsible for his actions. This is because of his unrestrained ambition, which, at the same time, is his tragic flaw. He allows his unchecked ambition to overpower his sense of right and wrong, and he commits many atrocious acts.
When he plots to murder Duncan, here is what Mabeth says:
The Prince of Cumberland! that is a step
On which I must fall down, or else o'erleap,
For in my way it lies. Stars, hide your fires;
Let not light see my black and deep desires.
(Act 1, Scene 4)
I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'erleaps itself
And falls on the other.
(Act 1, Scene 7)
From these quotes, it is clear that Macbeth is governed by his unrestrained ambition.
When he decides to have Banquo killed, Macbeth is also the one to blame because he chooses to believe in the witches' prophecy, and he believes he must get rid of Banquo and his son since Macbeth's position as the king could be jeopardized by Banquo's descendants:
For Banquo's issue have I filed my mind;
For them the gracious Duncan have I murder'd;
Put rancours in the vessel of my peace
Only for them... (Act 3, Scene 1)
...fears in Banquo stick deep...
There is none but he
Whose being I do fear: and, under him,
My Genius is rebuked...
(Act 3, Scene 1)
There are many more examples which illustrate that Macbeth relies on his perilous ambition to achieve his goals. He is motivated by his ambition and by his fear of retaining his power. Anyone who dares imperil his plans is automatically seen by Macbeth as the one who must be eliminated as soon as possible.
Here are a few quotes that reveal that Macbeth does have free will:
"if chance will have me King, why chance may crown me / Without my stir" (I, iii, 143-145)
" Stars, hide your fires; / Let not light see my black and deep desires" (I, iv, 50-510).
"I have no spur / To prick the sides of my intent, but only / Vaulting ambition" (I, vii, 25-27).
"I dare do all that may become a man: / Who dares do more is none" (I, vii, 47-48).
"I am settled, and bend up / Each corporal agent to this terrible feat. (I, vii, 79-80).
"The bell invites me. / Hear it not, Duncan, for it is a knell / That summons thee to heaven, or to hell" (II, i, 62-64)
"To be thus is nothing, but to be safely thus / Our fears in Banquo stick deep" (III, i, 48-49).