The Greek adjective sumpsuchos (σύμψυχος) is a compound of sun (together) and psuchē (soul, life), meaning literally 'same-souled' or 'united in soul.' It appears only once in the New Testament (Philippians 2:2) and captures the deepest kind of spiritual unity — not merely agreement of opinion but a shared inner life.
Paul's appeal in Philippians 2:2 is the fullest expression of Christian community: 'make my joy complete by being like-minded, having the same love, being one in spirit and of one mind (sumpsuchoi).' This unity flows not from organizational conformity but from sharing the same Spirit, the same love for Christ, and the same self-emptying humility demonstrated in Christ's incarnation (2:5–11). The word's depth — soul-union — echoes Jonathan and David's covenant ('the soul of Jonathan was knit to the soul of David', 1 Samuel 18:1). In Christ, believers share a deeper bond than human friendship: union through the Holy Spirit.