René-Louis Baire

René-Louis Baire was a French mathematician born in Paris in 1874 to a poor working family. He won a scholarship, entered the École Normale Supérieure and earned his doctorate in 1899 with a thesis on functions of real variables. That thesis contained the Baire category theorem, a result about complete metric spaces that became a standard tool in analysis and topology and gave rise to the classification of functions now named for him. He taught at Montpellier and then at Dijon, where he became professor of analysis in 1907. Delicate health kept interrupting his work, and after a leave in 1914 he lived mostly around Lake Geneva until he retired from Dijon in 1925.