This paper deals with the semantics of OCS dobr'' and blag'' in the translation of tetraeuangelion, compared with the semantics of their Greek correlates kalós, agathós and hrēstós. It points out the semantic changes which occurred in creating Slavic theological terminology. OCS dobr'' is an evaluative of the physical aspect of a notion, including its function, while blag'' through the process of semantic transposition acquired the meaning 'good in a spiritual sense'. This distinction reflects the Christian dual articulation of the world. This research reveals that a change of a cultural model induces semantic changes, be they 'natural' or consciously created in the development of certain terminologies, as witnessed here by Old Church Slavo...