4:5 one faith. All people, even atheists, have faith in something. The Christian faith, however, is the only saving faith (Ephesians 2:8). It is an understanding faith (Hebrews 11:3), a justifying faith (Romans 5:1), a purifying faith (Acts 15:9), a living faith (Galatians 3:11), a stable faith (II Corinthians 1:24), and a triumphant faith (I John 5:4). But this true faith may be rare on earth when Christ returns (see note on Luke 18:8).
4:5 one baptism. Whether this “one baptism” refers to Spirit baptism or water baptism has been extensively argued. Since both aspects of baptism are taught in the Bible, with water baptism being the visible sign and testimony to the Spirit’s baptism, and since no modifying words or phrases are attached to the word here to identify it as one or the other, it is probable that both aspects are in view, it being implicit that both go together in one unifying reality. See notes on I Corinthians 12:13 and Romans 6:3-5.