‘In loving thee thou know’st I am forsworn’: so begins the antepenultimate sonnet in William Shakespeare’s Sonnets – there are still two more to go in the sequence – but the last sonnet to advance a new argument. (The final pair are more of a coda to the overall cycle.) Sonnet 152 is not one of the most famous or memorable sonnets Shakespeare wrote, and some commentators (such as Don Paterson in his enjoyable Reading Shakespeare’s Sonnets: A New Commentary) have condemned it as misogynistic. Some words of analysis may help to shed light on this curious poem. First, though, here’s the text of Sonnet 152:
In loving thee thou know’st I am forsworn,
But thou art twice forsworn, to me love swearing;
In act thy bed-vow broke, and new faith torn,
In vowing new hate after new love bearing:
But why of two oaths’ breach do I accuse thee,
When I break twenty? I am perjured most;
For all my vows are oaths but to misuse thee,
And all my honest faith in thee is lost:
For I have sworn deep oaths of thy deep kindness,
Oaths of thy love, thy truth, thy constancy;
And, to enlighten thee, gave eyes to blindness,
Or made them swear against the thing they see;
For I have sworn thee fair; more perjured eye,
To swear against the truth so foul a lie!
Shakespeare begins Sonnet 152 by addressing the Dark Lady. Prior to this point in the Sonnets, the weird love triangle has developed between Shakespeare, the Fair Youth (a young, blond-haired man), and the Dark Lady (an older, married woman with a darker complexion and hair). In the first two lines of this sonnet, Shakespeare tells the Dark Lady: ‘In loving thee thou know’st I am forsworn, / 
But thou art twice forsworn, to me love swearing’: in other words, ‘You know that in loving you when I’m already in love with another, I’m breaking my promise to them. But it’s worse for you, Dark Lady, because you’re breaking two promises when you swear your love for me.’
The rest of the sonnet elaborates on this argument. We might paraphrase its meaning as follows: ‘After you recently married your husband, you have broken or “torn” the vow to share your bed with him and no other, and thus have committed yourself to hatred of those vows after swearing to love.
‘But you might very well say to me [Shakespeare continues in line 5], how do I have the nerve to accuse you of breaking two vows, when I have broken twenty? After all, every time I swear my love to you I am misusing you, because I don’t have any faith in you to keep your vows any more.’
Then, in the third quatrain (lines 9-12), Shakespeare continues his tirade against the Dark Lady: ‘I have told everyone how kind, true, loving, and faithful you are, and to make you seem better than you are [“enlighten” here is probably a play on the idea of her as the “Dark” Lady; i.e. he’s whitewashing her less than spotless reputation], I deliberately turned a blind eye to your faults.’
In the sonnet’s concluding couplet, Shakespeare declares: ‘I have told everyone how beautiful you are. My eye has perjured itself, because it has inspired me to tell this egregious lie.’
‘In loving thee thou know’st I am forsworn’ is a bitter sonnet, and it may well leave a bitter taste in the mouth. After all, Shakespeare is effectively saying that because he’s been sleeping with a married woman, he is jealous and thinks she’s false and can’t be trusted. Oh, and she’s ugly, too. What did he ever see in her? Hardly the Bard’s finest hour, we might say.
‘In loving thee thou know’st I am forsworn’: forsworn to whom, one wonders? Given the love triangle between the poet, the Fair Youth, and the Dark Lady, we’re tempted to say it’s the young man. However, Shakespeare was, after all, a married man, and Anne Hathaway was back in Stratford. As Stephen Booth points out in Shakespeare’s Sonnets (Yale Nota Bene)
