After a night together, a lover imagines how his partner will justify leaving in the morning. She might claim they are no longer the same people who made those vows, or argue that promises sworn in fear of Love’s anger can be broken, or that contracts between lovers, mere shadows of true marriages, only bind until sleep unties them. Her own faithlessness will force her to lie in order to seem true. The speaker calls her a ‘vain lunatic’ for these slick evasions, then pulls back: he could dispute and defeat her arguments, but he won’t, because by tomorrow he might be thinking the same way. The mood is witty and weary, alive with Donne’s pleasure in mental fencing, yet tinged with a shrug. The real twist isn’t her inconstancy—it’s his total, unashamed admission that he’s just as fickle.
Woman's Constancy — Summary
Now thou hast loved me one whole day, Tomorrow when thou leav'st, what wilt thou say? Wilt thou then antedate some new made vow? Or say that now We are not just those persons, which we were? Or, that oaths made in reverential fear Of Love, and his wrath, any may forswear? Or, as true deaths, true marriages untie, So lovers' contracts, images of those, Bind but till sleep, death's image, them unloose? Or, your own end to justify, For having purposed change, and falsehood, you Can have no way but falsehood to be true? Vain lunatic, against these 'scapes I could Dispute, and conquer, if I would, Which I abstain to do, For by tomorrow, I may think so too.