 The beloved, whose beauty Shakespeare idolizes here, is given the gift of immortality by the poet; the first two quatrains primarily address different ways in which the physical beauty of the material world inherently dims, fades, and/or falls short of ideal beauty at some point.In the third quatrain the poet presents his beloved with the gift of immortality in his lines of verse.The changing rhymes emphasize the dualist nature of beauty (how those things which are beautiful in their prime inevitably grow old, fade, and die), while the alternating pattern provides continuity.