"Painters teach us to see," Vincent van Gogh wrote to his brother Theo. But when Vincent's contemporaries looked at him, many of them saw only a madman -- "dressed like a scarecrow wandering in the fields with canvases under one arm and paintbrushes under the other." But Vincent followed his passion and listened to the lessons nature taught him about light, shadows, shapes, and colors. And now that "madman" is one of the most famous painters in the...