The third quatrain no longer focuses on the mutability of summer, but it speaks of the nearly eternal nature of the memory of the beloved. When the speaker assures his beloved that her “eternal summer shall not fade,” (9) he is using summer as a metaphor for her beauty. Using the word “fade” facilitates the comparison of the abstract notion of a summer’s day to the concrete person of the beloved because fading is a quality of light. Similarly, when the speaker writes of the beloved entering the “shade” (10) of death, he is expanding on the use of the metaphor and reinforcing the poem’s primary conceit. When the speaker boasts that his beloved will not suffer the same fate as a summer’s day because he has committed her to “eternal lines,” (12) he adds the theme of poetry itself to a sonnet that had previously been a love poem. Shakespeare gives his beloved immortality through poetry that God did not give to a summer’s day