Provide an example of a good thesis about ambition in Macbeth.

Ambition is certainly one of the dominant themes in Macbeth, and the play especially deals with the perils of unrestrained ambition which our hero, Macbeth, harbors. When analyzing ambition and its impact on others in the play, it would be useful to focus on the hero of the play, Macbeth. On many occasions, Macbeth states that it's solely his ambition to become the king which prompts him to forfeit his soul and become the indescribable...

Ambition is certainly one of the dominant themes in Macbeth, and the play especially deals with the perils of unrestrained ambition which our hero, Macbeth, harbors. When analyzing ambition and its impact on others in the play, it would be useful to focus on the hero of the play, Macbeth. On many occasions, Macbeth states that it's solely his ambition to become the king which prompts him to forfeit his soul and become the indescribable villain, devoid of conscience. My thesis would sound something like this --  In Macbeth, ambition is presented as a perilous force, which, when unrestrained, forces an individual to disintegrate under its influence.

Macbeth is aware that ambition is the one force driving him towards killing Duncan:

 I have no spur
 To prick the sides of my intent, but only
 Vaulting ambition, which o'erleaps itself
 And falls on the other.

In addition to the witches' prophecy, which only intensifies Macbeth's ambition, and Lady Macbeth's constant persuasion to get rid of Duncan, Macbeth admits that his plan to kill Duncan emanates from his surreptitious ambition:

 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.

Macbeth's ambition proves to be quite unrestrained, and once he commits the first crime, the murder of Duncan, he cannot stop. He murders anyone who could potentially imperil his position as the king of Scotland. His ambition to remain unbeatable and untouchable makes him an irredeemable sinner, whose newly embraced role as a tyrannous and sinister leader robs him of sanity and humanity.

Eventually, the very same ambition which Macbeth succumbs to at the beginning of the play leads to his imminent annihilation at the end of the play.