Axisymmetric

He is a paper-cutting artist who only cuts one pattern in his life - symmetrical butterflies. People said he was good at his craftsmanship, but no one ever asked why. When he got old, he took on an apprentice. The apprentice asked: "Master, why are butterflies always symmetrical?" He said: "Because love is an axis of symmetry. You are here, she is over there, and it is complete when you cut it out." The apprentice asked: "What about the master's wife?" He did not answer, but took out a piece of yellowed paper-cut from the bottom of the box. It unfolded to reveal a butterfly with half of its wings, and the other half was torn away. He said: "She took her other half with her when she left. All my life, I have been waiting for her to give her wings back."