The leader of the Realist movement was Gustave Courbet.

The leader of the Realist movement was Gustave Courbet. He defined Realism as a "human conclusion which awakened the very forces of man against paganism, Greco-Roman art, the Renaissance, Catholicism, and the gods and demigods, in short against the conventional ideal."how was this a revolution in the art world?

Fried, Michael. (1990). Courbet's Realism. The University of Chicago Press, Chicago