Determine what is being discussed in Sonnet #18.

Sonnet 18 is arguably the most famous of the sonnets, its opening line competitive with "Romeo, Romeo, wherefore art thou Romeo?" in the long list of Shakespeare's quotable quotations. Here the theme of the ravages of time again predominates; we see it especially in line 7, where the poet speaks of the inevitable mortality of beauty: "And every fair from fair sometime declines." But the fair lord's is of another sort, for it "shall not fade" - the poet is eternalizing the fair lord's beauty in his verse, in these "eternal lines."