“If you knew how I paid for that, translating Aquinas for Crocus,” Ikaros said. “I lost almost all my sight. I couldn’t read anything, or see much of anything at all. But all I have brought with me is perfectly innocuous—no, I suppose you’re right. I have a Jewish commentary on Philolaus and the Pythagoreans which would be forbidden here. I read it in Bologna when I was a student, and then when I was in the Enlightenment and I wanted to refer to it again I found it didn’t exist anymore. The copy I read must have been the last one, and then it was destroyed. Knowledge can be so fragile.”

“So you went to Bologna and stole the book?” Sokrates asked.

“I didn’t steal it! I had it copied. And I paid for him to make two copies and only collected one, so I doubled the chance of it surviving—though it may be that it was destroyed in the sack because the copyist had it and not the library.” Ikaros sighed. “Time. Freedom of action. It’s not an abstract problem.”

“No, it’s of vital importance,” Sokrates agreed. “How much can be changed and how much is fixed?”

“Necessity prevents the gods from being in the same place twice, and it prevents a lot of change. Change is easiest where nobody is paying attention, no gods and nobody recording anything. It gets harder the more attention there is. And it gets harder the more significant it is.”

“Who determines the significance?” Sokrates asked.

“Necessity,” Ikaros said, shrugging.

We came to the end of Hilfa’s street, where it crossed the road down to the harbor and up to the Old City. “We’re going this way now,” Marsilia said, gesturing uphill to where the bulk of the walls loomed. “Sleep well, everyone. I’ll see you tomorrow on the boat, Jason, Hilfa. I hope to see you again soon, Sokrates.”

“Come to Thessaly tomorrow and we can talk more,” Ikaros said

“Joy to you,” Sokrates said, and Hilfa and I echoed him. Standing on the corner we were in the full blast of the wind. But Thetis hesitated.

“I’m sorry I was so emotional,” she said. “I know it’s un-Platonic giving way like that. But it was a shock, and today has been rough. I’m not a philosopher, after all, and—”

“Not a philosopher!” Sokrates said, drawing himself up. “What nonsense. You were asking some of the best questions. It’s one of the silliest things about this ridiculous system, I’ve always said so, classifying people so young, trying to fix them unchangeably in place as if everyone is one thing and one thing only, Golds over here, Irons over there.”

“But I love my work,” Thetis objected. “And I’d be terrible at running the city!”

“Don’t you love wisdom too? Who said you had to be a philosopher full-time?” Sokrates demanded.