To live, you must die? No; to die, you must live. Dying is a result of the function of living, but dying is not the only result of the function, and nor does it have only one value. e.g. A robot, that cannot die, will die eventually, because it will malfunction one day. A biological being that has gained immortality, will die eventually, because it cannot survive every potential disaster in it's eternal life time. A being of pure energy, that cannot die, will live forever and never die. This does not mean there is no function of life.