Complex sentence: He is often spoken of in German works as the author of the "territorial system," or Erastian theory of ecclesiastical government; but he taught that the state may interfere with legal or public duties only, and not with moral or private ones.
Split into simpler sentences: He is often spoken of in German works as the author of the "territorial system," or Erastian theory of ecclesiastical government. But he taught that the state may interfere with legal or public duties only, and not with moral or private ones.