2001: A Space Odyssey (Space Odyssey #1)

by Arthur C. Clarke

In their explorations, they encountered life in many forms, and watched the workings of evolution on a thousand worlds. They saw how often the first faint sparks of intelligence flickered and died in the cosmic night. And because, in all the galaxy, they had found nothing more precious than Mind, they encouraged its dawning everywhere. They became farmers in the fields of stars; they sowed, and sometimes they reaped. And sometimes, dispassionately, they had to weed.