He does, however, promise that her "everlasting summer will not fade" (line 9). In making such a vow, he verifies that "summer" is symbolic of beauty; his lover's beauty will never fade, as would all other natural beauty, since he is saving it, and her, in the poem's "everlasting lines" (12). The idea of an everlasting summer comes from ancient poetry. The most famous example is from Theocritus' Idylls, which include several hundred verses written by various poets over a period of about one thousand years. One passage of Idyll XVII reads: "Eternal spring for those whose love endures / through every change of season and each year's progression." It's not clear from this quotation exactly what kind of spring Theocritus has in mind, but it probably isn't a wintery one. The word he uses here, chrestos, can mean either "season" or "year," and considering the lack of specificity in the quotation, it's easy to see how people have interpreted it as meaning an everlasting summer. People have also read deeper meanings into the poem than Theocritus probably intended. For example, some scholars believe that he is referring to a kind of marriage contract where both parties agree that if one party dies, then the other remains forever.