His eyes dwelt upon Oliver for an instant very keenly, like a physician’s eyes, impersonal and observing. Absently he reached for his stylus and the note pad. And as he moved, Oliver saw a familiar mark on the underside of the thick, tanned wrist.

“Kleph had that scar, too,” he heard himself whisper. “And the others.”

Cenbe nodded. “Inoculation. It was necessary, under the circumstances. We did not want disease to spread in our own time-world.”

“Disease?”

Cenbe shrugged. “You would not recognize the name.”

“But if you can inoculate against disease—” Oiver thrust himself up on an aching arm. He had a half-grasp upon a thought now which he did not want to let go. Effort seemed to make the ideas come more clearly through his mounting confusion. With enormous effort he went on.

“I’m getting it now,” he said. “Wait. I’ve been trying to work this out. You can change history? You can! I know you can. Kleph said she had to promise not to interfere. You all had to promise. Does that really mean you could change your own past—our time?”

Cenbe laid down his pad again. He looked at Oliver thoughtfully, a dark, intent look under heavy brows. “Yes,” he said. “Yes, the past can be changed, but not easily. And it changes the future, too, necessarily. The lines of probability are switched into new patterns—but it is extremely difficult and it has never been allowed. The physio-temporal course tends to slide back to its norm, always. That is why it is so hard to force any alteration.” He shrugged. “A theoretical science. We do not change history, Wilson. If we changed our past, our present would be altered, too. And our time-world is entirely to our liking. There may be a few malcontents there, but they are not allowed the privilege of temporal travel.”

—Henry Kuttner & C. L. Moore (as Lawrence O’Donnell), Vintage Season

This science fiction novella from 1946 could just as easily have been titled Forever Human.

For me, the most powerful moment in the history of scripted television occurs at the end of “Knowledge or Certainty”, episode 11 of J. Bronowski’s The Ascent of Man.

I owe it as a scientist to my friend Leo Szilard, I owe it as a human being to the many members of my family who died at Auschwitz, to stand here by the pond as a survivor and a witness. We have to cure ourselves of the itch for absolute knowledge and power. We have to close the distance between the push-button order and the human act. We have to touch people.

And with that, Dr. Bronowski walks into the pond, bends at the knees, puts his hand into the water and brings up a hand full of muck. Into this pond were flushed the ashes of four million people.

A halcyon day, please.