Kirsh" is indeed an abbreviation of "Krishna." It is rendered as "Krish" in The Van Rijn Method, p. 253.
Schuster subverts Ivanhoan theology by introducing the Kaballah. Part of his argument is that:
before the creation, no thinking, speaking creatures existed;
therefore, God's existence lacked the element of being observed and comprehended;
therefore, it was incomplete;
but the perfect God cannot be incomplete;
therefore, it was necessary for Him to create conscious beings that would be able to know Him.
The idea is that the Ivanhoans are unused to thinking outside their orthodoxy but some of them want to so dissension can be sown. But they need to hear Schuster's ingenuous arguments only to discard them! Surely God is believed to know and comprehend Himself? And why accept the premise of a perfect God in the first place?
I do not understand the description of the wheelless wagon at the end of the story but why was Falkayn able to think of the constant-width polygon when the Engineer was unable to?
In "The Three-Cornered Wheel," Falkayn is seventeen;
in "Wingless," his grandson, Nat, grows up and befriends Ythrians on Avalon;
in The People Of The Wind, their descendant, Tabitha Falkayn, grows up among Ythrians on Avalon;
in The Day Of Their Return, generations later, an Avalonian Ythrian spies on Aeneas;
in "Starfog," Daven Laure contacts descendants of Aenean rebels in another spiral arm -
- and that, unfortunately, is as far as the History of Technic Civilization extends.