From the 1860s on, critics increasingly speak of literary "Naturalism". The expression is imprecise, and was frequently used disparagingly to characterize authors whose chosen subject matter was taken from the working classes and who portrayed the misery and harsh conditions of real life. Many of the "naturalist" writers took a radical position against the excesses of romanticism and strove to use scientific and encyclopedic precision in their novels (Zola spent months visiting coal mines for his "Germinal", and even the arch-realist Flaubert was famous for his years of research for historical details). Hippolyte Taine supplied much of the philosophy of naturalism: he believed that every human being was determined by the forces of heredity and environment and by the time in which he lived. The influence of certain Norwegian, Swedish and Russian writers gave an added impulse to the naturalistic movement.