"You yourself created this Town. You made everything here. The Wall, the River, the Woods, the Library, the Gate, everything. Even this Pool. I've known all along."
"Then why did you not tell me sooner?"
"Because you'd only have left me here like this. Because your rightful world is there outside." My shadow sits down in the snow and shakes his head from side to side. "But you won't listen, will you?"
"I have responsibilities," I say. "I cannot forsake the people and places and things I have created. I know I do you a terrible wrong. And yes, perhaps I wrong myself, too. But I must see out the consequences of my own doings. This is my world. The Wall is here to hold me in, the River flows through me, the smoke is me burning. I must know why."

What It Means

This is a placeholder explanation generated by the low-overhead model. It interprets ""You yourself created this Town. You made everything here. The Wall, the River, the Woods, the Library, the Gate, everything. Even this Pool. I've known all along."
"Then why did you not tell me sooner?"
"Because you'd only have left me here like this. Because your rightful world is there outside." My shadow sits down in the snow and shakes his head from side to side. "But you won't listen, will you?"
"I have responsibilities," I say. "I cannot forsake the people and places and things I have created. I know I do you a terrible wrong. And yes, perhaps I wrong myself, too. But I must see out the consequences of my own doings. This is my world. The Wall is here to hold me in, the River flows through me, the smoke is me burning. I must know why."" in the context of "Chapter 40, Birds" to mean that wisdom is timeless.