I'm writing an essay on free will vs. fate in Macbeth. (I went with free will.) What three points could I grab from this thesis...

If the three witches are to be believed in the role of the
“fate sisters,” Macbeth’s own ambition precedes the proclamations of the witches on the
heath in act 1 scene 3. The witches only served as mirrors on which Macbeth could see
his own mind.

Macbeth’s long soliloquy in act 1 scene 7
reveals how Macbeth examines all the pros and cons of the murder of Duncan. He is
clearly self-divided, drawn asunder by the contrary pulls of his “vaulting ambition” and
his moral scruples. His unlawful ambition seems to get the better of his imaginative
conscience.

It is again Macbeth himself who chooses to kill
Banquo and his son, Fleance, though Banquo didn’t pose any threat to Macbeth’s power and
authority. Fleance was on the hit-list only because of the prophecy of the witches as
regards Banquo.

Macbeth’s decision at the end of the failed
Banquet  to meet the witches is yet another instance of his “free will.” By meeting the
witches and receiving another set of prophecies, Macbeth virtually enhances his
doom.

Even if the tragic downfall of Macbeth appears as
pre-destined, it is Macbeth himself who catalyzes the tragic outcome by his act of “free
will.”