Love is of course a major theme of this play where love (and its changes) seem to drive so much of the action. However, what is interesting to me is what the play says about love. The most profound expression that attempts to define what love is comes from Helena in her soliloquy at the end of Act I scene 1 where she decides to tell Demetrius about Hermia's plans to elope with Lysander:
Things base and vile, holding no quantity,
Love can transpose to form and dignity.
Love looks not with the eyes, but with the mind,
And therefore is wing'd Cupid painted blind...
And therefore is Love said to be a child,
Because in choice he is so oft beguil'd.
Love, therefore, Helena says, is blind, acts without reason and is often savage in its actions. She, of course, is the character who would know about the savagery of love, as she has been "won" by Demetrius, who then spurned her in his pursuit of Hermia. It is therefore especially poignant that these key words are given to Helena in the play.
Of course, the rest of the play goes on to prove Helena exactly right - characters left right and centre fall in love with others, changing their affections with incredible ease and rapidity. In fact, there is an argument that the ending of the play - often seen by critics as representing a more mature, lasting love - might not be that stable after all. Considering all that has past and the way that the Athenian males in particular have shown their true colours (in terms of their fickleness and their lack of constancy), a discerning reader/audience is left with some very hard questions about the steadfastness of their affections now. Love has indeed been shown to act without reason and logic and in a very cruel way - therefore the illusory stability that the play ends with perhaps is yet another example of a midsummer night's dream - the love that is here today may fade tomorrow, and perhaps as an audience we are left with a profound, almost disturbing uncertainty about love and its capacity to wound and hurt.