Throughout the sonnets, Shakespeare’s references to “substance” allude to the work of Plato, who viewed the world through the binary of “shadow” versus “substance.” According to Plato, the reality we perceive is false, a collection of ever-changing images. Below shadow—or “show,” as Shakespeare puts it in this line—lies “substance,” the stratum of true, constant forms which constitute the world. Physical beauty is a shadow, subject to change and decay. The speaker’s hope is to capture in verse the youth’s undying substance.

“Leese” means to lose. In this couplet, the speaker argues again for the distillation of beauty. If a flower is distilled it can meet with winter and “still lives sweet.” It loses its “show,” or physical outward appearance, but it does not lose its substance, or the essence of the beauty. Here, the speaker argues that beauty exists outside the physical realm in an idealized space.

“But” marks a rhetorical turn in the poem that signals the final couplet. This couplet does not offer a new argument or a universal truth but rather returns to the logic of line 8 in order to reiterate the importance of distillation.

“What it was” is an ambiguous phrase. By using this question word, Shakespeare simultaneously tells us nothing about the quality of the lost beauty and inspires an image in the reader’s head. By not qualifying the lost beauty with description, the reader must replace the words with their own meaning, or image.

“It” in this context is the substance of the beauty. This line completes the speaker’s thoughts on the distillation of beauty: without distillation, the beauty and memory of the beauty will be lost. Within this argument the speaker ironically displaces the beauty. He is no longer talking about the physical referent but the distillation of that beauty, his words about the youth or the collective memory of the youth. In this way, the speaker suggests that beauty can only truly exist when it is pulled out of time and context; the truth of beauty is the memory of its substance rather than its actual physical form.

“Bereft” means forcibly deprived or robbed. Reading this line within the context of the two that came before, the speaker claims that without the “distillation” of beauty, beauty and its effect will be lost. This is his argument for the need to distill and preserve beauty.

The image of summer’s distillation operates on three levels. On one level, the image is that of a glass vial of rosewater. On another level, the youth’s essence—or “substance”—is trapped forever; he becomes a prisoner watching life carry on outside his confines. On a third level, the very poem itself can be seen as the “walls of glass” which encase the youth. Each line of poetry is a “wall” that must be seen through in order to discover the meaning within. The poem’s meaning, of course, is “liquid”: open to interpretation and change, impossible to pin down.

These lines compare the fair youth to a summer rose whose essence is distilled as rosewater. The metaphor of distillation draws on the poem’s nature imagery while touching on the theme of meta-poetics—poetry about poetry. In the shift from summer to winter, the youth’s external form will die. If distilled, however, his essence will live on.

“Lusty” in this context means joyful, merry, or lively. The speaker juxtaposes “lusty” with the “frost” here to collapse the time between the joyful summer and barren winter. He uses this imagery to demonstrate how quickly life, youth, and beauty can become bareness and decay.

A central theme in Shakespeare’s Sonnets is the passage of “never-resting time.” It is the ephemerality of life that necessitates the very project of the sonnets: to distill the beloved through poetry, thus protecting him from the ravages of time.

This serves as an example of a chiasmus, a phrase in which a key word is repeated in a reversed or repurposed form. The play on words depends on two definitions of “fair.” The youth is “unfair” in the sense that his actions are morally unjust. Yet he is also “fair” in the sense that he is beautiful. Indeed, his beauty and his cruelty are inextricably linked.

The fair youth’s eyes take on the metaphorical role of “tyrants,” thus becoming both objects and subjects. As representations of his beauty, his eyes draw in the gaze of admirers. In turn, his eyes captivate those same admirers in tyrannical fashion. The sonnets often characterize the youth as cruel, wielding his beauty in malicious ways.

“Lovely gaze” refers to the youth’s gaze, which is both beautiful and tempered. This gaze is so beautiful, so refined, that it attracts the eyes of everyone in the room. However, this “lovely gaze” could also be that of the speaker gazing on the youth. The “lovely gaze” then becomes the gaze of the lover looking at his beloved and recognizing that “every eye” dwells in this gaze.

Often in Shakespeare’s sonnets, the subject of a phrase is spread across two or three lines of poetry. In these lines, the “hours’ shape the youth’s “lovely gaze” with gentle work. “Gentle work” refers both to kindness or tenderness and the noble class. In other words, the youth’s gaze was kindly shaped by hours or shaped by social expectations of the noble classes.

The speaker opens the poem with a reference to “those hours,” a stretch of time left unspecified. The speaker assumes the poem’s addressee, the beloved fair youth, knows of “those hours.” This gestures at a private space between the speaker and love object, creating an intimate tone.