"I was child," she said again after a moment. "But I remember--I remember things _different_ from this. Air ... heat ... light ... how do I live here?" Again I felt amazement at its intelligence; (and it suddenly occurred to me that astronomy and nuclear physics must have been taught in Sorn's "elementary schools"--else that _my years_ and _atom explosion_ would have been all but impossible). And now this old, old creature, remembering back three thousand years to childhood--probably to those "elementary schools"--remembering, and defining the differences in environment between _then_ and _now_; and more, wondering at its existence in the different _now_-- And then I got my own thinking straightened out. I recalled some of the things we had learned about the Zen. Their average lifespan had been 12,000 years or a little over. So the Zen before me was, by our standards, about twenty-five years old. Nothing at all strange about remembering, when you are twenty-five, the things that happened to you when you were seven ... But the Zen's question, even my rationalization of my reaction to it, had given me a chill. Here was no cuddly teddy bear. This creature had been born before Christ! She had been alone for three thousand years, on a chip of bone from her dead world beneath a sepulchre of stars. The last and greatest Martian civilization, the _L'hrai_, had risen and fallen in her lifetime. And she was twenty-five years old. "How do I live here?" she asked again. I got back into my own framework of temporal reference, so to speak, and began explaining to a Zen what a Zen was. (I found out later from Yurt that biology, for the reasons which follow, was one of the most difficult studies; so difficult that nuclear physics actually _preceded_ it!) I told her that the Zen had been, all evidence indicated, the toughest, hardest, longest-lived creatures God had ever cooked up: practically independent of their environment, no special ecological niche; just raw, stubborn, tenacious life, developed to a fantastic extreme--a greater force of life than any other known, one that could exist almost anywhere under practically any conditions--even floating in midspace, which, asteroid or no, this Zen was doing right now. The Zens breathed, all right, but it was nothing they'd had to do in order to live. It gave them nothing their incredible metabolism couldn't scrounge up out of rock or cosmic rays or interstellar gas or simply do without for a few thousand years. If the human body is a furnace, then the Zen body is a feeder pile. Maybe that, I thought, was what evolution always worked toward. "Please, will you kill me?" the Zen said. * * * * * I'd been expecting that. Two years ago, on the bleak surface of Eros, Yurt had asked Engstrom to do the same thing. But I asked, "Why?" although I knew what the answer would be, too.