cause, a cause we cannot explain; in other words, a magical cause. Shakespeare personifies that cause with the faeries appearing in the play. They dance about, they prick the lovers on towards each other, they have them lose sight of one another, falling prey to fear and panic. As for the clueless Bottom, they cover him with blissful touches and loving kisses.
Adding to the mystery, these erotic agents are themselves the playthings of love. Oberon directs Puck to magically manipulate Titania's feelings, but why doesn't he just dump his queen if she is such trouble? Because he loves her. Oberon is as much subject to his passions as we humans are. Sex, like magic, is self-substantial.
King Lear—Existentialism three hundred years before Sartre