Epei is a causal and inferential conjunction appearing 26 times in the New Testament, primarily in Paul's epistles and Hebrews. It introduces the logical or causal basis for a preceding statement: 'since it is so,' 'because this is the case,' 'otherwise...' It is the glue of theological argument — the word that links the 'therefore' conclusions of Paul to their doctrinal foundations. Without epei, the 'since' and 'because' of covenant logic disappears.
Though a grammatical particle, epei carries significant theological weight because it marks cause-and-effect relationships in the unfolding argument of the Gospel. In Hebrews 2:14, 'Since [epei] the children have flesh and blood, he too shared in their humanity' — incarnation is necessitated by the reality of human nature. Romans 3:6 uses it to defend God's righteousness: 'Since [epei] otherwise, how could God judge the world?' In 1 Corinthians 14:16, it grounds liturgical practice in the logic of intelligibility. Epei trains the mind to follow theological reasoning: God acts as He does because of who He is and what He has promised.