"But don't you see?" insisted Howell angrily. "There can be no source other than a future time! You can't send short waves through three-dimensional space to a given spot and not have them interceptible between. Anyhow, the Compubs wouldn't work it this way! They wouldn't put us on guard! And an extra-terrestrial wouldn't pretend to be a human if he honestly wanted to warn us of danger! He'd tell us the truth! Physically and logically it's impossible for it to be anything but what it claims to be!" Graves said doggedly: "But a broadcast originating in the future is impossible!" "Nothing," snapped Howell, "that a man can imagine is impossible!" "Then imagine for me," said Graves, "that in 2180 they read in the history books about a terrible danger to the human race back in 1972, which was averted by a warning they sent us. Then, from their history-books, which we wrote for them, they learn how to make a transmitter to broadcast back to us. Then they tell us how to make a transmitter to broadcast ahead to them. They don't invent the transmitter. We tell them how to make it--via a history book. We don't invent it. They tell us--from the history book. Now imagine for me how that transmitter got invented!" "You're quibbling," snapped Howell. "You're refusing to face a fact because you can't explain it. I say face the fact and then ask for an explanation!" "Why not ask them," said Graves, "how to make a round square or a five-sided triangle?" * * * * * Sergeant Bellews pushed to a spot near Betsy. He put down his now-linked Mahon machines and began to move away some of the recording apparatus focused on Betsy. "Hold on there!" said Howell in alarm. "Those are recorders!" "We'll let 'em record direct," said the sergeant. * * * * * Lecky spoke feverishly in support of Bellews. But what he said was, in effect, a still-marveling description of the possibilities of Mahon-modified machines. They were, he said with ardent enthusiasm, the next step in the historic process by which successively greater portions of the cosmos enter into a symbiotic relationship with man. Domestic animals entered into such a partnership aeons ago. Certain plants--wheat and the like--even became unable to exist without human attention. And machines were wrought by man and for a long time served him reluctantly. Pre-Mahon machines were tamed, not domestic. They wore themselves out and destroyed themselves by accidents. But now there were machines which could enter into a truly symbiotic relationship with humanity. "What," demanded Howell, "what in hell are you talking about?" Lecky checked himself. He smiled abashedly: "I think," he said humbly, "that I speak of the high destiny of mankind. But the part that applies at the moment is that Sergeant Bellews must not be interfered with."