With Sonnet 138 William Shakespeare takes a step back and reflects on how both he and his mistress in their relationship with each other are effectively living a lie which they both actively conspire to maintain: she pretends to be faithful to him although she fully knows that he knows that she obviously isn't, and he goes along with it when she treats him as if he were an innocent young lover who not only is still in his prime but who is also uneducated in matters of love, both of which she similarly knows not to be the case.