“Now let me ask you again. Will you let me cross this bridge safely, enter the ship, and then leave safely when I’ve finished my work?”

Odinex gave no answer. It was as if the question had not been asked.

Umbo had studied enough of the programming of the ship’s computers and the expendables that he understood what was happening. “You can’t make a prediction because you don’t know what I intend to do.”

“Correct.”

“Can you tell me what to avoid doing in order to keep you from needing to kill me?”

“Giving you a list of forbidden actions will only make it easier for you to act in a forbidden way.”

“But not giving me the list makes it impossible for me to avoid doing a forbidden thing.”

“You can avoid doing a forbidden thing by not entering the starship.”

“So if you push me off the bridge and I fall and you don’t rescue me, I can’t violate the ship.”

“That would be one solution.”

“Is it the one you’re planning to use?”

“Yes.”

“Thank you for answering my question honestly.”

“I tell the truth,” said the expendable.

Umbo wanted to ask, Now tell me how to get onto the starship. But of course the expendable would see through a ruse like that; there was no point in trying it.

Besides, Umbo had been studying starship design for the best part of a year. There were things he knew.

“Odinex, are you malfunctioning?”

“I am not.”

“How do you know?”

“Because my self-auditing software reports that my functions are normal.”

“Odinex, is your self-auditing software malfunctioning?”

A long pause. “I do not know.”

“Odinex, will you run diagnostics on your self-auditing software?”

“I will when you are not present.”

“I am not a threat,” said Umbo, annoyed now that the expendable wasn’t going to be as easy to control as he had hoped.

“You are a threat,” said Odinex.

“On what basis do you regard me as a threat?”

“The person you call Swims-in-the-Air has told me you are a threat.”

“But that person is not human.”

“She is more human than you are,” said Odinex.

Umbo pulled the knife from his clothing and displayed the jeweled hilt. “Do you recognize this knife?”

“Yes,” said Odinex.

“Are the jewels in the hilt faithful copies of the jewels of control?”

“Yes.”

“Smaller, but faithful.”

“Yes.”

“Do they function like the jewels of control?”

“Yes.”

“Because I possess these jewels, can I be certified as commander of this vessel?”

“In the absence of any other commander, you could be certified.”

“Is there another commander?”

“Rigg Sessamekesh is the commander of all the vessels on the planet Garden, and all the orbiters, and all the expendables.”

“So these jewels cannot be used to take his place.”

“He is not dead,” said Odinex.

A dark thought came into Umbo’s heart. He drove it away. “One of these jewels is the jewel of control for this ship alone, yes?”

“Yes.”

“Can I use it to be certified as the commander of this vessel, as long as I don’t contradict the orders of Rigg Sessamekesh?”

“With his consent, yes.”

“But he is not human,” said Umbo.

“Human status is not required to be in command of the vessel.”

An interesting loophole. But there was another. “I am a descendant of Ram Odin.”

“After generations of intermarriage, everyone now alive in both Ramfold and Odinfold is a descendant of Ram Odin. Everyone is a descendant of all the colonists. After eleven thousand years, it could not be otherwise.”

“Was Ram Odin human?”

“Yes.”

“Were his children human?”

“Yes.”

“What were their names?”

Odinex listed them, and then said, “I see your point.”

“Were their children human?”

“Yes. I see your point.”

“At which generation did they cease to be human?” asked Umbo.

“I see your point.”

“But do you accept it as a valid definition of humanity? As the primary definition?”

A pause. “I do.”

“So the argument of genetic continuity is superior to the argument of accumulated genetic drift and alteration.”

“It is,” said Odinex.

“May I come aboard?”

“You may.”

Umbo stepped onto the bridge and strode briskly across.

He did not so much hear the expendable come along behind him as feel the wind of his coming. Then he felt Odinex’s hands on his back, picking him up and shoving him toward the edge of the bridge.

Umbo shifted in time to a few seconds earlier. Now he was standing at the point where Odinex had taken hold of him, but now Odinex was two meters farther back on the bridge, preparing to seize him, while Umbo’s previous self was one meter away, looking surprised to see this new version of himself.

The expendable was even more surprised, though his face showed nothing.

“Which of us do you need to kill?” asked Umbo.

The earlier Umbo turned around and faced the expendable. Now that Odinex was not throwing Umbo off the bridge, that version of Umbo did not need to time-shift. Both Umbos continued to coexist, standing side-by-side on the bridge.

The Umbo who had shifted now stepped back two paces and shifted again. Now he could see both earlier versions of himself facing Odinex on the bridge. “Is this how Ram Odin was duplicated, Odinex?” asked Umbo. “Obey no one but me, expendable.”

The expendable stood transfixed.

Umbo turned and walked swiftly through the door into the ship.

Then he ran.

He knew the layout of the ship, knew exactly where the control room was, and knew, from Rigg’s account of it, what to do with the jewels. What he didn’t know was which of the jewels controlled this ship.

He stood at the verifying machine, holding the hilt of the knife into the field. “Is the jewel of control for this vessel present here?”

“It is,” said the ship’s computer.

“Rigg Sessamekesh gave me this knife,” said Umbo. “I take command of this vessel as Rigg’s subordinate.”

There was a slight hesitation. “Did Rigg authorize this procedure?” asked the ship’s computer.

“Is this the jewel of control?” asked Umbo.

“Yes.”

“Did Rigg Sessamekesh give this jewel to me as part of the knife?”

“He did.”

“I take command of this vessel as Rigg’s subordinate.”

Another hesitation. “Certified.”

“Command all expendables attached to this ship to obey me and cause me no harm.”

“Done.”

“Is the expendable still on the bridge with the other two copies of me?”

“No,” said the ship’s computer. “He killed them both and is on his way to this place.”

Umbo shuddered. “Command him to come into this room walking backward. He is forbidden to look at me.”

Moments later, Odinex backed into the room.

“Stop,” said Umbo.

The expendable stopped.

“This ship, and all the equipment of this ship, will hereby define ‘human being’ as ‘organism descended in an unbroken line from the colonists of one or more of the ships commanded by Ram Odin on their voyage to Garden.’ Do you understand?”

“Yes,” said the expendable.

“Yes,” said the ship’s computer.

“Am I human?”

“Yes,” they both answered without hesitation.

“Who can change this definition?”

“You can,” said the ship and the expendable.

“Let one speak for both,” said Umbo.

The ship’s computer fell silent.

“You and Rigg Sessamekesh can change this definition,” said Odinex.

“Who else?”

“No one.”

Umbo knew this was not true, but also knew that the computers couldn’t lie.

“Is there a procedure by which someone else can gain the authority to change this definition without my or Rigg’s consent?”

“Yes.”

“Can you disable all procedures that would allow us to be superseded?”

“No.”

“Can I disable them?”

“Yes,” said the expendable.

In this situation, Umbo didn’t trust simple answers. “And if I do, what will be the consequences?”