The analogy is meant to show parallels between two sets of words. Fertile is to arable as vague is to clouded. If you understand either pair it can be used to decipher the meaning of the other pair you don't know.
Answer:
The quote means to fall in love with someone without caring about their looks. If you follow your heart instead of your eyes you can find true love. In the play the some of the characters fall in love based on how the other person looks but when they follow their heart instead falling for who's prettier they find their true love.
Let me know if this helps and good luck!
