Pathos is a persuasive technique where the person trying to persuade uses an appeal to emotion. There are several examples of pathos in Macbeth, but Lady Macbeth’s diatribe about bashing her child’s brains out is one of the most obvious ones.
I have given suck, and know(60)
How tender ’tis to love the babe that milks me:
I would, while it was smiling in my face,
Have pluck'd my nipple from his boneless gums,
And dash'd the brains out (Act 1, Scene 7)
In this scene, Lady Macbeth is trying to convince her husband to kill King Duncan. She wants to convince him that she is strong, and if she could do it so can he. At the same time, Shakespeare uses this line to help convince us that Lady Macbeth is truly nuts. She is so violent that she brings up this terrible image of nursing a child and then bashing its brains out, losing the audience’s sympathy as she gains Macbeth’s respect.
An appeal to emotions is one way to persuade. In this case, the use of pathos in this image works two ways. It persuades Macbeth, but it also convinces the audience.
Pathos is an emotional appeal and Shakespeare uses emotion to humanize his murderous lead characters. For example, Lady Macbeth experiences intense guilt over the murders she has encouraged and sanctioned. When we watch her sleepwalking and compulsively washing her hands, crying, "out damned spot! out I say ...," trying in vain to scrub out the blood and thus metaphorically trying to cleanse her soul of murder, we realize she is less a monster than a deeply flawed human being. While it is hard to feel sorry for her, we do feel her pain. All of us, if we are honest with ourselves, have blithely committed some mistake or gotten in over our heads in something we thought we could handle (though usually something much more minor than murder), only to later have regrets and remorse over what we have done. We can relate to Lady Macbeth, because we understand what it feels like to make a mistake.
Likewise, we feel for Macbeth earlier in the play, when he consciously recognizes that in agreeing to murder Duncan, his good king, he has set out on a path of murder and bloodshed that he won't ever get out from under. As he makes the decision to cross the line, we wish fervently he wouldn't because our emotions have been engaged by this basically decent man who is blinded by his ambition and a false sense of destiny.