With Sonnet 142 William Shakespeare picks up on the notion of 'sin' employed in the last line of the previous sonnet, and now juxtaposes this sin or sinful love of his for his mistress with her supposed 'virtue' in rejecting this love for being sinful, while simultaneously undermining any suggestion that she is in fact virtuous by asking her to just take a long, hard look at herself and her own behaviour, from which she will readily recognise that it is just as bad, if not in fact much worse.

The sonnet thus continues the poet's double-edged approach to wooing his mistress, by on the one hand expressing his wish to have sex with her, while on the other hand also mildly rebuking her for having sex with other men, or, to be more precise, while refusing to be rebuked by her for wanting to have sex with her, when she herself is liberally sleeping around.