The final two lines sees Shakespeare place his argument on what true love is in a position beyond reproach. In which he states that if any of what he has said 'be error' (116 ), then he 'never writ, nor no man ever loved.' (116 ). This statement provides Shakespeare an unbreakable get out clause, in that if any of the sonnet is proved to be untrue or disagreed with then not only does he deny any accountability of having written those untrue statements but also affirms that no man has ever experienced love, therefore placing the accuser in a position of weakness as they would be criticising his work without the grounding of experience. This perhaps shows itself to be a vivid example of how firmly Shakespeare believed what he had written. In that by inserting the final two lines in the manner that he did he made the argument put forward by the sonnet perfect and irreproachable to any attempt to spoil it from man or the outside world, much in the same way that he argued that love itself was.
But has the poet really abandoned the idea of encouraging the fair lord to have a child? Some scholars suggest that the "eternal lines" in line 12 have a double meaning: the fair lord's beauty can live on not only in the written lines of the poet's verse but also in the family lines of the fair lord's progeny. Such an interpretation would echo the sentiment of the preceding sonnet's closing couplet: "But were some child of yours alive that time / You should live twice; in it and in my rhyme." The use of "growest" also implies an increasing or changing: we can envision the fair lord's family lines growing over time, yet this image is not as readily applicable to the lines of the poet's verse - unless it refers only to his intention to continue writing about the fair lord's beauty, his verse thereby "growing." On the other hand, line 14 seems to counter this interpretation, the singular "this" (as opposed to "these") having as its most likely antecedent the poet's verse, and nothing more.