Seismic Shifts in Subject and Style

Why did subject and style in art change so dramatically over the course of the 19th century - from Madame Recamier, by Jacques-Louis David (1800) to Luxe, Calme et Volupte by Matisse (1904)? We'll look for an explanation through a combination of art analysis and philosophical detection. Artistic trends are not the result of a collective consciousness working its will. Such trends are simply the styles that a majority of artists chooses to embrace. Each of those artists, in turn, makes his own ch