After a moment the Archeologist continued, "My reconstruction of their history, subsequent to the laying down of the cache, has been largely hypothetical. I can only guess at the reasons for their decline and fall. Supplementary material has been very slow in coming in, though we are still making extensive excavations at widely separated points. Here are the last reports." He tossed the Explorer a small metal-leaf pamphlet. It flew with a curiously slow motion. "That's what struck me so queer right from the start," the Explorer observed, putting the pamphlet aside after a glance. "If these creatures were relatively advanced, why haven't we learned about them before? They must have left so many things--buildings, machines, engineering projects, some of them on a large scale. You'd think we'd be turning up traces everywhere." "I have four answers to that," the Archeologist replied. "The first is the most obvious. Time. Geologic ages of it. The second is more subtle. What if we should have been looking in the wrong place? I mean, what if the creatures occupied a very different portion of the Earth than our own? Third, it's possible that atomic energy, out of control, finished the race and destroyed its traces. The present distribution of radioactive compounds throughout the Earth's surface lends some support to this theory. "Fourth," he went on, "it's my belief that when an intelligent species begins to retrogress, it tends to destroy, or, rather, debase all the things it has laboriously created. Large buildings are torn down to make smaller ones. Machines are broken up and worked into primitive tools and weapons. There is a kind of unraveling or erasing. A cultural Second Law of Thermodynamics begins to operate, whereby the intellect and all its works are gradually degraded to the lowest level of meaning and creativity." * * * * * "But why?" The Explorer sounded anguished. "Why should any intelligent species end like that? I grant the possibility of atomic power getting out of hand, though one would have thought they'd have taken the greatest precautions. Still, it could happen. But that fourth answer--it's morbid." "Cultures and civilizations die," said the Archeologist evenly. "That has happened repeatedly in our own history. Why not species? An individual dies--and is there anything intrinsically more terrible in the death of a species than in the death of an individual?" He paused. "With respect to the members of this one species, I think that a certain temperamental instability hastened their end. Their appetites and emotions were not sufficiently subordinated to their understanding and to their sense of drama--their enjoyment of the comedy and tragedy of existence. They were impatient and easily incapacitated by frustration. They seem to have been singularly guilty in their pleasures, behaving either like gloomy moralists or gluttons.