Joseph Mallord William Turner (1775-1851), the English Romantic artist who lifted landscape and seascape painting to new and enthralling heights will never cease to amaze, inspire and make us question what we thought we knew about painting, about what colored pigment on canvas can do. “Turner’s Modern World” at the Boston Museum of Fine Art allows viewers to revisit and rediscover this modern ‘Oracle’, as the philosopher Deleuze would refer to him.