Caroline Spurgeon is quite a bit harder on Arthur Brooke (the writer of The Tragicall Historye of Romeus and Juliet (1562), which was probably Shakespeare's only source for Romeo and Juliet) in her classic work of criticism, Shakespeare's Imagery and What it Tells Us from 1935, than even I was the other day when I contrasted Shakespeare's philosophical sophistication with Brooke's heavy-handed moralizing. In giving credit for the fact that Shakespeare took from Brooke the idea of using recurring images of light and darkness, she wrote the following: "He took the idea from the last place we should expect, from the wooden doggerel of Arthur Brooke, and the germ of it is in the sing-song line in which Brooke describes the attitude of the lovers: 'For each of them to other is as to the world the sun.'" I'm not sure I find that line, or Brooke's writing overall, quite as bad as Spurgeon does, but it is surprising to realize that Shakespeare didn't necessarily require a good source (i.e. an excellent writer such as Plutarch, for example) from which to fashion a masterpiece.