Three days, of course, is a long time to sustain an emotion, and, when Toloth returned to Teresa's cage the following Wednesday, his qualms about the Yeerk conquest of Earth had completely dissipated. He had not actually refuted his own arguments, of course; he had simply decided that anything so contradictory to the ideas he had believed all his life must be somehow erroneous. It was not a strictly logical thought process, but then Yeerks – as their history of emotional instability would indicate – are not a strictly logical race.

"You remember me, I trust," he said.

Teresa nodded.

"As you will recall," said Toloth, "I left rather hastily last time…"

"That's all right," said Teresa. "I didn't mind."

Toloth blinked. "I was not apologizing," he said.

Teresa's face hardened, and her tone grew sarcastic. "Oh, no, of course not," she said. "Forgive me for thinking that you might be."

Then, abruptly, she shut her mouth – shut it so tightly, in fact, that Toloth could see her lips whiten with loss of blood – and took a deep breath. When she spoke again, it was in a much softer and more measured tone.

"I'm sorry," she said. "I'm not always as calm as I should be about these things. Please forgive me."

In his entire life, Toloth had never had a host apologize to him for anything. It caught him off guard, and he mumbled the first meaningless courtesy that came to mind, which happened to be a Desbadeen phrase meaning "My claws are retracted".

As Teresa did not know the Desbadeen language, she was somewhat at a loss for a response. Conversation, accordingly, languished for a number of seconds.

"What was it you wanted to say?" said Teresa finally.

Toloth seemed to come out of a daze. "What?"

"You started to say something about the last time we met," said Teresa. "Then I interrupted you, and…"

"Ah, yes," said Toloth. "The last time we met, yes. If I remember correctly, you had just finished explaining to me how your God was three persons in one nature, and how one of these persons – the one you call Jesus, I believe – had become the son of a woman named Mary."

Teresa nodded. "Yeah, that sounds about right."

"Now why," said Toloth, "would a god do that?"

Teresa swallowed. She had never met anyone who was quite so gifted at coming to the point as this Yeerk.

"Jesus became the Son of Mary," she said slowly, "because we were sinful creatures, and we needed to be made right with God."

Toloth cocked his head. "And if Jesus took the form of a human, that would accomplish that?" he said.

"Well, it wasn't just the form of a human He took," said Teresa. "He took our whole nature upon Himself. He became as weak and vulnerable as a human, while at the same time staying as powerful as God."

Toloth frowned. "Is this another idea like the multiple-persons-in-a-single-nature one?" he asked.

"Um… sort of," said Teresa. "Actually, it's the reverse of that idea: instead of having three persons who all share one nature, with Jesus you have two natures combined in one person. So if you asked who he was, you would only get one answer, but if you…"

Toloth nodded impatiently. "Thank you, Teresa, I do remember how the distinction works," he said.

Calm, Teresa, the young apologist told herself as she felt her bile rise again. Stay calm. He's a Yeerk, he's spent his whole life dominating other life-forms, he has certain mannerisms that are going to annoy you, but at bottom he's as much an image of God as you are. Remember that, and don't start snapping at him just because he's not as polite as his host.

"Right, okay," she said. "So Jesus was both God and a human. And that was important, because humans had gotten the world into a real mess. See, back when the first humans were created, the universe had been completely flawless; there was no suffering, no death, no evil, nothing. All of Nature existed in perfect harmony with the Source of Eternal Goodness Who had created it."

"It must have been pleasant," Toloth murmured.

"I would assume so," said Teresa, "though I wasn't there, of course."

Toloth frowned in puzzlement. "What does that have to do with anything?" he said. "Of course existing in perfect harmony with a source of eternal goodness would be a pleasant experience. You don't need to experience it personally to realize that."

"Right, of course," said Teresa hastily, making a mental note not to rely too much on human humor when speaking to this particular inquirer. "The problem was, though, that God had given the first humans – their names were Adam and Eve – a way to disrupt that harmony. It seems there was a certain fruit-bearing tree in the middle of the garden where they lived, and God had told them that, if they ever ate the fruit off it, they would bring death into the world."

Toloth blinked. "Wait," he said. "Your God, your source of eternal goodness, provided the means for evil to enter the world. Is that what I am to understand?"

Teresa hesitated, and spent some moments considering the question before slowly responding, "Um… yeah, I guess so. But He didn't make them choose it, He just…"

Toloth waved his hand. "Never mind whether he made them choose it," he said. "If he provided the opportunity for evil to exist, then to that extent he was involved in its creation. Correct?"

"If you wanted to put it that way, I guess you could," Teresa admitted.

"All right," said Toloth – and it seemed to Teresa that there was a note of either triumph or relief, or possibly both, in his voice. "Now, if your God is the source of all goodness, and also the source of all evil, how is he distinguishable from nothing at all? Don't the scientists teach us that two contraries, when brought together, annihilate each other?"

"But God isn't the source of all evil," said Teresa.

"You just said he was," said Toloth, with that same curious note of a relieved sneer.

Teresa shook her head. "No, I didn't," she said. "I said that God permitted evil. And He does. But permitting something isn't the same thing as causing it."

"Isn't permitting evil itself an evil?" rejoined Toloth.

"No."

"Why not?"

In truth, Teresa had no idea. All she knew was that "God is not a tempter of evils, and he tempteth no man", and that therefore, if God permitted evil to exist, that permission could not itself be evil. In short, she was operating on faith, and hoping that her reason would come along for the ride – and, to the consternation of Rationalists everywhere, it did.

"Well, what's the alternative?" she said. "If you don't admit even the possibility of evil, then no one can ever reject evil in order to choose good. And that's the best kind of good there is, so wouldn't it be supremely evil to prevent it from ever happening?"

Slowly, the look of condescending triumph faded from Toloth's face, to be replaced by an expression of reluctant uncertainty. "Do you mean to say," he said slowly, "that good cannot be fully good unless it threatens itself with annihilation?"

"Phrase it however you want," said Teresa. She was speaking very quickly now, for fear that she would lose whatever was being poured into her if she stopped to think for too long. "You can say that God only permits evil so He can make good out of it. You can say that love that's compelled isn't really love. You can say that freedom is a greater good than existence. However you say it, it's true."

As soon as the last two sentences were out of her mouth, she suddenly remembered what sort of creature she was talking to. She clapped her mouth shut, and glanced up uncertainly at the enormous Hork-Bajir-Controller in front of her cage.

Toloth's expression had grown cold and unreadable. Without saying a word, he rose from his place on the ground, turned his back on the young apologist, and walked away from the row of cages.

Teresa flopped down onto the floor of her cage and sank her head into her hands. I'm sorry, God, she said silently. I tried, I really did…

And, for the second time in four days, a thought seemed to come to her from somewhere outside her mind. Peace, child, it said. You have done all that was needed for now. Leave the rest for another time.