In Act 1, Scene 7 of William Shakespeare's "Macbeth," Lady Macbeth expresses her determination to achieve her ambitions. She says that she would dash the brains out of her own child if she had sworn to do so, rather than breaking her promise to Macbeth about committing murder. This statement underscores the depth of Lady Macbeth's commitment to the plan and her willingness to go to extreme lengths to achieve her goals.
Lady Macbeth says she would have smashed her own child's skull against a castle wall if she had to -
"How tender βtis to love the babe that milks me.
I would, while it was smiling in my face,
Have plucked my nipple from his boneless gums
And dashed the brains out, had I so sworn as you
Have done to this."
She chillingly declares she would dash her own baby's brains out if necessary to uphold her commitment to helping Macbeth gain power, demonstrating her ruthless ambition.
She asserts that she would go to extreme lengths for the sake of ambition and her husband's advancement.
This assertion is made to provoke Macbeth into acting on their plan to murder King Duncan, which emphasizes her ruthless determination and the violent lengths she is willing to go to in order to secure their desired position.