The voice of Van Gogh Expressionist art involves a dangerous tension of the spirit. We feel that Grunewalt cannot have been entirely sane. But the frenzied writhings, the Cathrine-wheel convoltions of Van Gogh are further out of control than anything in El Greco, and in fact painfully similar to the paintings of actual madmen. Perhaps this is one reason why they have proved so popular. The assul..