“The same thing might be said of stones, yet there are statues.” For all his aspect of despair (and his was a sadder face by far than my friend Jonas’s), something tugged at the corners of his lips.

“That is well put. You have no scientific training, but you are better taught than you realize.”

“On the contrary, all my training has been scientific — although it had nothing to do with these fantastic speculations. What are you?”

“A great seer. A great liar, like every man whose foot is in a trap.”

“If you’ll tell me what you are, I’ll endeavor to help you.”

He looked at me, and it was as if some tall herb had opened eyes and shown a human face. “I believe you,” he said. “Why is it that you, of all the hundreds who come to this tent, know pity?”

“I know nothing of pity, but I have been imbued with a respect for justice, and I am well acquainted with the alcalde of this village. A green man is still a man; and if he is a slave, his master must show how he came to that state, and how he himself came into possession of him.”

The green man said, “I’m a fool, I suppose, to put any confidence in you. And yet I do. I am a free man, come from your own future to explore your age.”

“That is impossible.”

“The green color that puzzles your people so much is only what you call pond scum. We have altered it until it can live in our blood, and by its intervention have at last made our peace in humankind’s long struggle with the sun. In us, the tiny plants live and die, and our bodies feed from them and their dead and require no other nourishment. All the famines, and all the labor of growing food, are ended.”