Medardo Rosso is not a name you are likely to know, but Renoir and Degas looked up to him as a friend who went in directions they would not have dared. Later artists, from the Italian Futurists to Brancusi, considered him a mentor. Rosso’s experiments gave courage to those who would abandon the rules of classicism, and who were ready to dissolve form. He was born in Turin in 1848, lived in Paris from 1889 to 1920, and then moved to Milan, where he died in 1928. Rosso has been periodically rediscovered, then forgotten again, then rediscovered again. At the Kunstmuseum Basel, a large and comprehensive exhibition offers a rare opportunity to immerse yourself in his haunting universe. —Nicholas Fox Weber