Why is the quote "Love looks not with the eyes, but with the mind, and therefore is winged Cupid painted blind" so important? This quote is found in...

Shakespeare writes about love a lot.  This
quote is about that theme, but what I like about this quote is that it doesn't support the
"love at first sight" notion.  In fact, the heroictakes sight completely out of the
love equation.  Shakespeare is telling his audience, through Helena, that love is a matter of
the heart.  It is more dependent on an emotional bond rather than a physical attraction.  The
idea is nothing new to Shakespeare.  He writes about the same thing in a couple of his sonnets.
  explains how his mistress is definitely not attractive, but he still loves her deeply.
 

And yet, by heaven, I think my love as
rare

As any she belied with false compare.

Sonnet 141 is along the same lines; however, it specifically mentions the eyes just
like Helena does in the play. 

In faith, I do not love
thee with mine eyes,
For they in thee a thousand errors note; 
But 'tis my
heart that loves what they despise,
Who in despite of view is pleased to
dote....

As a general rule of love, I feel that the quote
is teaching an important lesson.  In terms of the play, the line foreshadows events to come.
 Most notably, the line foreshadows Titania falling in love with Bottom despite the fact that he
has a donkey's head.  

Another example of how this quote shows true love
being blind can be found through the character of Demetrius. When the play begins, he's in love
with Hermia, and Helena indicates that the main reason is because Hermia is prettier.  By the
end of the play, Demetrius has found his true love in Helena.  He was looking for love with his
eyes; however, he wasn't finding true love.  As soon as he stopped relying on his eyes, he was
able to discover the love that he and Helena share.