1824-1871 1853-1900 1871-1944 19thcentury 20thcentury biography bulgakov doctrines doctrinesorthodoxeasternchurch feodor history historyrusskai͡apravoslavnai͡at͡serkovʹ russia russkai︠a︡pravoslavnai︠a︡t︠s︡erkovʹ sergiĭ solovyov sovietunion theologians theology vladimirsergeyevich булгаков сергейниколаевич