In the earlier sonnets, the poet's main concern was to persuade the youth to marry and reproduce his beauty in the creation of a child. That purpose changes here in Sonnet 17, in which the poet fears that his praise will be remembered merely as a "poet's rage" that falsely gave the youth more beauty than the youth actually possessed, thus expressing an insecurity about his poetic creations that began in the preceding sonnet.
This disparaging tone concerning the sonnets is most evident in line 3, in which the poet characterizes his poetry as a "tomb." Such death imagery is appropriate given the frequent incorporation of time, death, and decay images throughout the first seventeen sonnets. Ironically, the poet, who has been so concerned about the young man's leaving behind a legacy at death to remind others of his priceless beauty, is now worried about his own future reputation. Will his poems be ridiculed by readers who disbelieve the poet's laudatory praise of the young man's beauty? Not, says the poet, if the youth has a child by which people can then compare the poet's descriptions of the youth's beauty to the beauty of the youth's child — now asking the youth to have a child in order to confirm the poet's worthiness.
The sonnet's concluding couplet links sexual procreation and versification as parallel activities: "But were some child of yours alive that time, / You should live twice — in it and in my rime." The poet's task is an endless struggle against time, whose destructive purpose can only be frustrated by the creation of fresh beauty or art, which holds life suspended.