How is ambition shown to be destructive through the character Macbeth?

When William Shakespeare's Macbeth is taught in high schools, one of the themes teachers tend to focus on is ambition. How the two main characters, Macbeth and his wife Lady Macbeth, react to to the effects of ambition-gone-wrong provides much of the play's drama.

In the beginning, Macbeth's ambition is tepid at best. He is tantalized by the idea of becoming king, but he doesn't seem committed to actually doing what must be done to...

When William Shakespeare's Macbeth is taught in high schools, one of the themes teachers tend to focus on is ambition. How the two main characters, Macbeth and his wife Lady Macbeth, react to to the effects of ambition-gone-wrong provides much of the play's drama.

In the beginning, Macbeth's ambition is tepid at best. He is tantalized by the idea of becoming king, but he doesn't seem committed to actually doing what must be done to achieve his goal (he says, “I have no spur to prick the sides of my intent”— in modern English, "I just can't make myself do it"). When Macbeth tries to back out of his plan to murder King Duncan, Lady Macbeth plays on her husband's ego by questioning his manhood.

After the murder of King Duncan, Lady Macbeth and Macbeth switch places, in a sense. She is haunted by guilt and wanders in her sleep, trying to wash imagined blood from her hands. Macbeth, on the other hand, just goes deeper into ambitious madness, killing Banquo and Macduff's family to preserve his own power. When Lady Macbeth kills herself, the guilt produced by her ambition has in a sense taken her life.

Ambition leads to Macbeth's downfall in a different way. He doesn't kill himself like Lady Macbeth, but when he learns of her death he essentially gives up on life:

Life is but a walking shadow, a poor player

That struts and frets his hour upon the stage

And then is heard no more; it is a tale

told by an idiot, full of sound and fury,

Signifying nothing.

After all of the terrible things Macbeth has done, he is left with nothing. Most importantly, he no longer sees a reason to live.