So this is how I'm viewing/ coping with our 2 part finale. Ep 17 was the true ending of Twin Peaks (as we the audience knew it). Coop leads Laura out of the woods and this sets off a chain of events. Laura is never killed and the growing horror we've seen unleashed on this town has been stopped. Coop no longer exists in this world because this world doesn't need a Coop. Just as we were about to get a nice neat ending Laura gets lost again. Ep 18 is a different show with a different premise. The archetype of Coop is still searching for Laura but not in the Twin Peaks world we've spent the last 26 years in. As Phillip showed, the owl/experiment symbol became the sign of infinity. Cooper is destined to fight and tame the forces of evil, it's his purpose. Cooper won the last fight, and he will probably always win... but the Black Lodge will always come back in some form or another. Episode 18 was very upsetting, but it helps me to think of 17 as the true finale of the show we've all loved. Ep 18 is the denouement of the story: in other realities the battle continues.