I looked back at him. For an instant he looked like a dappled animal with big eyes, and then he was himself again. “Well, it seems very strange to me to be saying these things, which are truths that everyone agrees about. Even in Lucia these days they accept limitations on the modes of music. I don’t think even in Sokratea, where they question everything all the time, they question that. If anyone had ever doubted it, the example of what happened with the Lucians proved that Plato was right about this.”

Hermes sat up a little and arched a brow. “Proved it? How?”

“Well, it’s obvious. They played music in the Mixolydian mode, and they tortured people to death and plagiarized. It led their souls away from justice.”

“It could be the other way around.”

I considered that for a moment, staring off at the trees again and the veins on the little yellow leaves. “I suppose it’s possible. The torture and plagiarism could have led to harmful music arising. But that’s no better.”

“There are a couple of good historical examples on Earth of changing the music and the whole culture changing. They’re much later than Plato though. One is Southern Gaul in the chivalric era, and the other is the phenomenon they call the Sixties.” He smiled. “They were both a lot of fun.”

“So you agree Plato was right?” I asked, looking directly into his eyes, which for an instant had red and yellow Saeli lids, looking strange in his human face.

“Well, maybe. But I think I’d get bored. And you’d be surprised how many people intoxicate themselves immoderately and eat things that are bad for them. Lots of people in other cultures don’t consider a party with quince paste and watered wine as exciting as you might.”

I thought about that, and wondered again about the humans on the ship. Would they be eating unhealthy food and drinking unmixed wine and listening to soul-destroying music? If so, how could we help them understand? What if they tried to introduce such things on Plato? Would there be people who would be tempted? Young people, feeling rebellious, who could find ammunition to do themselves real and lasting harm? I could hear a chirping music now, sounding like a small child learning to sing. I looked around for it and saw the bird, sitting on one of the branches, its beak open and its throat distended. I had of course read about birds singing. The music it made was safely in the Dorian mode. “I don’t find the idea of food that’s bad for me at all appealing.”

“That’s because you’ve never had any.” He was smiling and watching me through half-lowered lids.

“Maybe. But I find the idea of music that’s bad for my soul terrifying,” I said honestly.