For 10 points, name this German mathematician whose namesake axioms of set theory were extended by Abraham Fraenkel.
This man theorized that if both chess players are rational, then a sequence of winning moves can be found using an algorithm, then developed a backward-induction algorithm still used in games of perfect information. He also proved Henri Poincaré's recurrence theorem, then used it to argue against the Second Law of Thermodynamics. This mathematician independently discovered Russell's paradox, and introduced the Axiom of Choice in his proof of the Well-Ordering Theorem. His best-known contribution may be a set of seven axioms including those of union, separation, and infinity. For 10 points, name this German mathematician whose namesake axioms of set theory were extended by Abraham Fraenkel.
This man theorized that if both chess players are rational, then a sequence of winning moves can be found using an algorithm, then developed a backward-induction algorithm still used in games of perfect information.
Ernst Friedrich Ferdinand {Zermelo}