After discussing the different means by which the fair youth’s beauty might be preserved, the speaker ends with a statement of the power of poetry. The poem reflects back on itself, for the speaker claims that “this gives life to thee.” “This” refers to this very sonnet. The separation between the poem and the world within the poem collapses. The speaker is the poet. Shakespeare employs this literary move throughout the sonnet sequence, referring often to the immortality of his own work. As long as his work continues to be read, Shakespeare’s claims ring true.

A normal Shakespearean sonnet uses an abrupt uptick in end rhyme in the final couplet, shifting from ABAB quatrains to a GG couplet. To this couplet Shakespeare adds dense internal rhyme. In line 13, “breathe” and “see” are connected through assonance; that they land on the stresses of line’s third and fifth beats, respectively, accentuates the connection. In line 14, “lives” and “gives” injects an additional perfect rhyme to the couplet. This abundance of internal rhyme underscore the speaker’s point about poetry’s power.

The use of “grow’st” at the end of the line reveals an additional interpretation of “lines.” The poem itself, with its power to immortalize the youth, attaches him to time as if he were a scion, a grafted plant shoot. Thus “eternal lines” can take on a literal reference to tree branches. This metaphor evokes once again the thematic use of the natural world while deepening the idea of poetry as procreation.

“Eternal lines” takes on multiple interconnected meanings. The “lines” can refer to lines of poetry, referring to the speaker’s desire to preserve the fair youth through verse. The “lines” can also refer to genetic lineage, another means by which the fair youth can preserve his own image through time. Shakespeare seems to be equating these two lines, artistic and genetic. In the preceding poems, the speaker urged the youth to procreate; now the speaker weighs the benefits of poetry as a means of passing on the youth’s essence.

This line evokes both Judeo-Christian and Greco-Roman conceptions of death. The “shade” can be read as a reference to Psalm 23: “Yea, though I walk through the valley of the shadow of death, I will fear no evil: for thou art with me.” This reference frames the youth’s life in spiritual terms: his fairness extends to his soul, and thus he is worthy of salvation. The personification of death is a device from Greco-Roman tradition, as is the use of “shade” as human soul. This separation of soul from body relates to the poem’s central theme. Physical beauty fades and dies, but the fair youth’s essence can be captured and memorialized through poetry.

In the poem’s third use of “fair,” we encounter a third meaning of the word. “Fair” now takes on the noun form, serving as a shortened version of “fairness.” The shifting use of the word is indicative of Shakespeare’s linguistic play. In a deeper sense, the changing definition of the word “fair” represents “nature’s changing course”—the passage of time that decays all fair things.

While the sun is said to “lease” its short summer period, the speaker here claims that the beloved has “possession” of his fairness, or beauty. Unlike the sun which has a “too short” lease on summer, the youth has eternal possession of his “fairness.” This difference demonstrates that the youth is a more substantial beauty than summer and furthers the speaker’s belief that he is better than a summer’s day. Youth’s possession also aligns him with the higher landowning class.

Throughout the sonnets, the speaker compares a lifespan to the changing seasons of the year. “Summer” represents the period of early adulthood while winter symbolizes old age and the end of one’s life.

The progression of verbs in this sonnet—shines, dimmed, declines, fade—reflects the passage of time. The speaker acknowledges that the summer’s day is transitory and uses this sequence of words to reflect the fading of brightness that happens over time.

Fairness fades as a result of both accidental decay as well as “nature’s changing course”—in other words, aging. The use of “untrimm’d” draws on a nautical metaphor: the adjustment, or trimming, of sails to fight the direction of the wind. Thus the “rough winds” in line 3 are reiterated, once again representing the unrelenting forces of nature.

Shakespeare uses “fair” in two senses. The first “fair” means “one who is fair,” or beautiful. In its second instance, “fair” is used in its typical form as an adjective. The line tells of the inevitable fading of physical beauty: on the surface, fair people will lose their fairness.

The “his” in this line refers back to the subject of the preceding line, the “too hot” eye of heaven, or sun. Unlike the Petrarchan sonnet which uses the blazon tradition to fragment the beloved, the speaker fragments the vehicle of comparison; the sun’s complexion is dimmed.

“Lease” is an example of the financial metaphors that occur throughout Shakespeare’s Sonnets. The legal language of this metaphor implies a bad deal: the summer’s “lease” was “all too short” and this bad deal causes the summer to be ephemeral. This negative depiction of summer is later contrasted by the positive depiction of the youth’s “possession” of fairness in line 10.

“Temperate” has a dual meaning here. It means both having a calm and even temperament, and “a period of time.” This description of the youth embodies not only his perfect character, but the ability of this perfection to outlast time. He is unconfined by the changing of the seasons.

Though the speaker initially rejects the blazon tradition, one could argue that he still compares his beloved to summer in order to show that the beloved is perfect. However, unlike a typical blazon, the speaker does not fragment the beloved into his distinct physical parts. He is treated as a whole person, “thou.”

Shakespeare uses the question that begins this sonnet to challenge and question Petrarchan tropes. Petrarchan sonnets generally compare each part of the beloved’s body to a larger concept or natural system. This trope, called the blazon tradition, was used to describe the beloved as the most beautiful, or perfect embodiment of beauty. The speaker uses the question here to reject this trope: he will not compare his beloved to a summer’s day because the beloved is more lovely and more temperate.

The beginning of this sonnet plays on the proverb “as good as one shall see in a summer’s day,” meaning “as good as the best there is.” The speaker is essentially asking, shall I compare you to the best of the best?