«O, from what power hast thou this powerful might
With insufficiency my heart to sway?».
Using a more rational tone than in the previous sonnet, the poet tries to understand why he cannot completely break from the woman. He shifts his approach, asking what incredible power the woman uses to enslave him; earlier he had asked himself what his own character flaws were that bound him to her.
O, from what power hast thou this powerful might
Again written as a series of questions to the woman, the poet asks the woman, “O, from what pow’r hast thou this pow’rful might / With insufficiency my heart to sway?” Contrary to all sense, the poet appeals for pity from his mistress. Her sexual powers have unbalanced his judgment and inflamed his imagination. Promiscuity, the least flattering thing about the woman, is what he loves.
English audio from YouTube Channel Socratica
Summary from Cliffsnotes.com