For example, the speaker’s lover “swears that she is made of truth.” In response, the speaker says: “I do believe her, though I know she lies.” This paradoxical statement shows that knowing the truth does not always affect what we choose to believe. The sonnet shows that what we know and what we think or believe sometimes diverges. She plays along, and this makes him happy: “in our faults by lies we flattered be.” Thinking versus Knowing He knows that his “days are the past the best.” Yet he recognizes that not everyone wants to admit how old they are when it comes to romantic matters: “age in love loves not to have years told.” This is why he never says openly to his lover that he is “old.” Instead, he falls for his lover’s lies because he thinks this shows him to be an “untutored youth” who is clueless about how the world works. The speaker of the poem is self-conscious about his age.
Letting himself be deceived is flattering because he can act like a young man again. In fact, they are both lying to each other: “simple truth suppressed.” The speaker chooses to “believe” his lover’s lies because it allows him to pretend to be younger than he is: only an inexperienced boy would choose to believe his lover is faithful to him when it is so obvious that she is not. The speaker likes to pretend that he is younger than he is. The lover swears that she is faithful to him. In Sonnet 138, the speaker and his lover deceive each other.