Giordano Bruno

Dominican friar from Nola who left the order, wandered the courts of Europe teaching a combinatorial art of memory, argued that the universe is infinite and holds innumerable worlds, and was burned in the Campo de' Fiori in 1600 after eight years of trial, having refused to recant. His sentencing line survives only through a bystander's letter (Gaspar Schoppe's), so hold it as reported, not recorded.

He stands at the head of three of this corpus's threads at once: the coincidence of contraries that Joyce built the Wake on (borrowed, honestly, from Nicholas of Cusa and pushed further), the many-worlds instinct that Borges and Wilson turned into fiction, and the memory palace — the ancestor of the very room you are standing in.