FTP, name this mathematician whose address at the 1900 International Congress of Mathematicians stimulated much of the work of the 20th century.
He invented the discipline of proof theory in an attempt to formalize all of mathematics.  His interest in formalism is evident in his earliest published work, where his proof of his Basis Theorem was criticized for being too purely abstract.  In addition to making modern algebraic geometry possible with his Basis Theorem and Nullstellensatz, he properly rigorized Euclid's axioms for plane geometry and showed how various non-Euclidean geometries followed from different modifications of these axioms.  FTP, name this mathematician whose address at the 1900 International Congress of Mathematicians stimulated much of the work of the 20th century.
He invented the discipline of proof theory in an attempt to formalize all of mathematics.  
David Hilbert