"What made you think of that at this particular time?" the engineer demanded.

"Maybe," the FBI man said, "there's no one fact or even cluster of facts about Sousa that prove to Genux-B he exists. Maybe it's all the facts. There may be just plain too many. The computer had found, on the basis of past experience, that when so much data exists on a given person, that person must be genuine. After all, a computer of the magnitude of Genux-B is capable of learning; that's why we make use of it."

"I have another fact I'd like to feed to it," the engineer said. "I'll type it out and you can read it." Reseating himself at the programming typewriter, he ground out one short sentence, then yanked the card from the bales and showed it to the rest of them. It read:

THE COMPUTER GENUX-B DOES NOT EXIST.

After a stunned moment, one of the FBI men said, "If it had no trouble in comparing the datum about Herbert Sousa with what it already knew, it certainly isn't going to have any trouble with this – and what's your point anyhow? I don't see what this accomplishes."

"If Genux-B doesn't exist," Stafford said, with comprehension, "then it can't send out a Red Alert; that's logically a contradiction."

"But it has sent out a Red Alert," the shortest of the FBI men pointed out. "And it knows it has. So it won't have any difficulty establishing the fact of its existence."

The engineer said, "Let's give it a try. I'm curious. As far as I can see ahead, no harm can be done. We can always cancel out the phony fact if it seems advisable."

"You think," Stafford asked him, "that if we feed it this datum it'll reason that if it doesn't exist it couldn't have received the datum to that effect – which would cancel the datum right there."

"I don't know," the engineer admitted. "I've never heard even a theoretical discussion as to the effect on a B-magnitude computer of programming a denial of its own existence." Going to the feed bracket of Genux-B, he dropped the card in, stepped back. They waited.

After a prolonged interval, the answer came over the output cable, which the engineer had tapped. As he listened through his headphones, he transcribed the computer's response for the rest of them to study:

ANALYSIS OF CONSTITUENT RE THE NONEXISTENCE OF GENUX-B MULTIFACTOR CALCULATING INSTRUMENTS. IF CONSTIT UNIT 340s70 IS TRUE, THEN:

I DO NOT EXIST.

IF I DO NOT EXIST, THEN THERE IS NO WAY I CAN BE INFORMED THAT MY GENERIC CLASS DOES NOT EXIST.

IF I CANNOT BE INFORMED IN THAT REGARD, THEN YOU HAVE FAILED TO INFORM ME, AND CONSTIT UNIT 340s70 DOES NOT EXIST FROM MY STANDPOINT.

THEREFORE: I EXIST.

Whistling with admiration, the shortest of the FBI men said, "It did it. What a neat logical analysis! He's proved – it's proved – that your datum is spurious; so now it can totally disregard it. And go on as before."

"Which," Stafford said somberly, "is exactly what it did with the datum filed with it denying that Herb Sousa ever existed."

Everyone glanced at him.

"It appears to be the same process," Stafford said. And it implies, he reasoned, some uniformity, some common factor, between the entity Genux-B and the entity Herb Sousa. "Do you have any of the charms, prizes, or just plain geegaws, whatever they are, that Sousa's gum machines dole out?" he asked the FBI men. "If so, I'd like to see them…"

Obligingly, the most impressive of the FBI men unzipped his briefcase, brought out a sanitary-looking plastic sack. On the surface of a nearby table he spread out a clutter of small glittering objects.

"Why are you interested in those?" the engineer asked. "These things have been given lab scrutiny. We told you that."

Seating himself, not answering, Stafford picked up one of the assorted trinkets, examined it, put it down, and selected another.

"Consider this." He tossed one of the tiny geegaws toward them; it bounced off the table and an obliging FBI agent bent to retrieve it. "You recognize it?"

"Some of the charms," the engineer said irritably, "are in the shape of satellites. Some are missiles. Some interplan rockets. Some big new mobile land cannons. Some figurines of soldiers." He gestured. "That happens to be a charm made to resemble a computer."

"A Genux-B computer," Stafford said, holding out his hand to get it back. The FBI man amiably returned it to him. "It's a Genux-B, all right," he said. "Well, I think this is it. We've found it."

"This?" the engineer demanded loudly. "How? Why?" Stafford said, "Was every charm analyzed? I don't mean a representative sample, such as one of each variety or all found in one given gum machine. I mean every damn one of them."

"Of course not," an FBI man said. "There's tens of thousands of them. But at the factory of origin we -"

"I'd like to see that particular one given a total microscopic analysis," Stafford said. "I have an intuition it isn't a solid, uniform piece of thermoplastic." I have an intuition, he said to himself, that it's a working replica. A minute but authentic Genux-B.

The engineer said, "You're off your trolley."

"Let's wait," Stafford said, "until we get it analyzed."

"And meanwhile," the shortest of the FBI men said, "we keep Genux-B inoperative?"

"Absolutely," Stafford said. A weird weak fear had begun at the base of his spine and was working its way up.

Half an hour later the lab, by special bonded messenger, returned an analysis of the gum-machine charm.

"Solid nylon," the engineer said, glancing over the report. He tossed it to Stafford. "Nothing inside, only ordinary cheap plastic. No moving parts, no interior differentiation at all. If that's what you were expecting?"

"A bad guess," one of the FBI men observed. "Which cost us time." All of them regarded Stafford sourly.

"You're right," Stafford said. He wondered what came next; what hadn't they tried?

The answer, he decided, did not lie in the merchandise with which Herb Sousa stuffed his machines; that now seemed clear. The answer lay in Herb Sousa himself – whoever and whatever he was.

"Can we have Sousa brought here?" he asked the FBI men.

"Sure," one of them said presently. "He can be picked up. Buy why? What's he done?" He indicated Genux-B. "There's the trouble right there, not way out on the Coast with some small-potatoes-type businessman working half the side of one city street."

"I want to see him," Stafford said. "He might know something." He has to, he said to himself.

One of the FBI men said thoughtfully, "I wonder what Genux-B's reaction would be if it knew we're bringing Sousa here." To the engineer, he said, "Try that. Feed it that nonfact, now, before we go to the trouble of actually picking him up."

Shrugging, the engineer again seated himself at the typewriter. He typed:

SACRAMENTO BUSINESSMAN HERB SOUSA WAS BROUGHT TODAY BY FBI AGENTS BEFORE COMPUTER COMPLEX GENUX-B FOR A DIRECT CONFRONTATION.

"Okay?" he asked Stafford. "This what you want? Okay?" He fed it to the data receptors of the computer, without waiting for an answer.

"There's no use asking me," Stafford said irritably. "It wasn't my idea." But, nevertheless, he walked over to the man monitoring the output line, curious to learn the computer's response.

The answer came instantly. He stared down at the typed-out response, not believing what he saw.

HERBERT SOUSA CANNOT BE HERE. HE MUST BE IN SACRAMENTO, CALIFORNIA; ANYTHING ELSE IS IMPOSSIBLE. YOU HAVE PRESENTED ME WITH FALSE DATA.

"It can't know," the engineer said huskily. "My God, Sousa could go anywhere, even to Luna. In fact, he's already been all over Earth. How would it know?"