Complex sentence: Politically, Eustathios was a supporter of emperor Manuel I. An original thinker, he sometimes praised such secular values as military prowess; he decried slavery, and believed in the concept of historical progress of civilization from a primitive to a more advanced state.
Split into simpler sentences: Politically, Eustathios was a supporter of emperor Manuel I. An original thinker, he sometimes praised such secular values as military prowess. He decried slavery, and believed in the concept of historical progress of civilization from a primitive to a more advanced state.