The Last Stone teaches that, because every act matters, one must never mistake discouragement for completion. 

As long as one true act remains possible - one page preserved, one song recorded on the Mystic Tape Deck, one artifact cataloged, one child taught the old stories - the reflection of the world is still capable of changing. The Last Stone is simply the name the Cloak gives to that final, indispensable act.

The recurring image of crystalline preservation is generally regarded as the earliest surviving expression of what later Bell philosophers termed the Doctrine of the Last Stone: the conviction that hope acquires its greatest significance only after every ordinary strategy has failed. The unnamed architects of the Ecuadorian repository are never portrayed as believing they could prevent the world's destruction. Their labor begins only after accepting that destruction had become inevitable.