▁a ▁city ▁as ▁a ▁determ ining ▁factor ▁in ▁its ▁ecc les iast ical ▁position ; ▁but ▁he ▁strongly ▁supported ▁its ▁dog m atic ▁decre es , ▁especially ▁when , ▁after ▁the ▁acc ession ▁of ▁Leo ▁I ▁the ▁Th ra cian ▁( 4 5 7 ), ▁there ▁seemed ▁to ▁be ▁a ▁disposition ▁toward ▁comprom ise ▁with ▁the ▁E ut ych ians . ▁ ▁Te aching ▁on ▁Christ ▁ ▁Leo ' s ▁writ ings ▁( both ▁the ▁ser m ons ▁and ▁the ▁letters ) ▁are ▁mostly ▁concerned ▁with ▁the ological ▁questions ▁concerning ▁the ▁person ▁of ▁Jesus ▁Christ ▁( Christ ology ) ▁and ▁his ▁role ▁as ▁medi ator ▁and ▁sav ior ▁( S ot eri ology ), ▁which ▁is ▁partially ▁connected ▁to ▁the ▁Council ▁of ▁Chal ced on ▁in ▁which ▁Roman ▁leg ates ▁participated ▁in ▁Leo ' s ▁name . ▁Sub sequently , ▁through ▁numerous ▁letters ▁addressed ▁to ▁b ish ops ▁and ▁members ▁of ▁the ▁imperial ▁family , ▁Leo ▁in cess antly ▁worked ▁for ▁the ▁propag ation ▁and ▁universal ▁reception ▁of ▁the ▁faith ▁in ▁Christ ▁as ▁defined ▁by ▁Chal ced on , ▁also ▁in ▁the ▁eastern ▁part ▁of ▁the ▁Roman ▁emp ire . ▁Leo ▁def ends ▁the ▁true ▁div inity ▁and ▁the ▁true ▁human ity ▁of ▁the ▁one ▁Christ ▁against ▁her et ical ▁one - s ided ness . ▁He ▁takes ▁up ▁this ▁topic ▁also ▁in ▁many ▁of ▁his ▁ser m ons , ▁and ▁over ▁the ▁years , ▁he ▁further ▁develop s ▁his ▁own ▁original ▁concepts . ▁A ▁central ▁idea ▁around ▁which ▁Leo ▁deep ens ▁and