quality:correction, stylistic:tone, quality:corruption, linguistic:paraphrasing
As a tragedy of character

At least since the days of Samuel Johnson, analysis of the play has centred on the question of Macbeth's ambition, commonly seen as so dominant a trait that it defines the character. Johnson asserted that Macbeth, though esteemed for his military bravery, is wholly reviled.

This opinion recurs in critical literature, and, according to Caroline Spurgeon, is supported by Shakespeare himself, who apparently intended to degrade his hero by vesting him with clothes unsuited to him and to make Macbeth look ridiculous by several exaggerations he applies: his garments seem either too big or too small for him – as his ambition is too big and his character too small for his new and unrightful role as king. After Macbeth is unexpectedly greeted with his new title as Thane of Cawdor as prophesied by the witches, Banquo comments:

New honours come upon him, Like our strange garments, cleave not to their mould, But with the aid of use

And, at the end, when the tyrant is at bay at Dunsinane, Caithness sees him as a man trying in vain to fasten a large garment on him with too small a belt:

He cannot buckle his distemper'd cause Within the belt of rule

while Angus sums up what everybody thinks ever since Macbeth's accession to power:

now does he feel his title Hang loose about him, like a giant's robe upon a dwarfish thief

Like Richard III, but without that character's perversely appealing exuberance, Macbeth wades through blood until his inevitable fall. As Kenneth Muir writes, "Macbeth has not a predisposition to murder; he has merely an inordinate ambition that makes murder itself seem to be a lesser evil than failure to achieve the crown." Some critics, such as E. E. Stoll, explain this characterisation as a holdover from Senecan or medieval tradition. Shakespeare's audience, in this view, expected villains to be wholly bad, and Senecan style, far from prohibiting a villainous protagonist, all but demanded it.

Yet for other critics, it has not been so easy to resolve the question of Macbeth's motivation. Robert Bridges, for instance, perceived a paradox: a character able to express such convincing horror before Duncan's murder would likely be incapable of committing the crime. For many critics, Macbeth's motivations in the first act appear vague and insufficient. John Dover Wilson hypothesised that Shakespeare's original text had an extra scene or scenes where husband and wife discussed their plans. This interpretation is not fully provable; however, the motivating role of ambition for Macbeth is universally recognised. The evil actions motivated by his ambition seem to trap him in a cycle of increasing evil, as Macbeth himself recognises:

I am in blood Stepp'd in so far that, should I wade no more, Returning were as tedious as go o'er.

While working on Russian translations of Shakespeare's works, Boris Pasternak compared Macbeth to Raskolnikov, the protagonist of Crime and Punishment by Fyodor Dostoevsky. Pasternak argues that "neither Macbeth or Raskolnikov is a born criminal or a villain by nature. They are turned into criminals by faulty rationalizations, by deductions from false premises." He goes on to argue that Lady Macbeth is "feminine... one of those active, insistent wives" who becomes her husband's "executive, more resolute and consistent than he is himself". According to Pasternak, she is only helping Macbeth carry out his own wishes, to her own detriment.