While melancholy is a state of vague dreaminess, never deep or intense, sadness is closed, serious, and painfully interiorized. One can be sad anywhere, but sadness grows in intensity in a closed space while melancholy flourishes in open spaces. Sadness almost always stems from a precise motive and is therefore concentrated, whereas there are no exterior causes for melancholy. I know why I am sad, but I do not know why I am melancholy.