Not all exchanges were harmless. A banker who treated the seam like a curiosity left a ledger open with figures that trusted no one’s arithmetic. By morning his accounts had inverted; debts became gifts, investments sprouted names of strangers who had needed them more. He left angry and richer in a coin he did not recognize. A scholar long in doubt brought an argument to the right wing and found his certainty hijacked by an opinion that belonged to his childhood self. He learned, to his dismay, that certainty could be a borrowed garment with moth holes.