Sonnet 138 is about a relationship between the speaker and his lover. The lover swears that she is truthful and faithful to the speaker. The speaker knows that she is lying but chooses to believe her anyway. He does this because he is anxious about his age. He thinks that if he acts naive and gullible he will appear younger than he is. In return, the lover pretends that the speaker is young, though she knows very well that his “days are past the best.” This pleases the speaker, though it does result in lies on both sides.
The speaker also has doubts. He wonders why his lover lies about cheating him. He also wonders why he does not just admit that he is old. Finally, he decides that believing in how things appear is the best habit lovers can have. Besides, old lovers do not want to have to admit their age. The sonnet ends with a double entendre (a sexual pun) on the word “lie”: the speakers both lie to each other and lie down together. It is lies that make their relationship, and their sex life, possible. It allows them to be “flattered” and forget their “faults.”
