word of God is efficacious, it does what it says it will do. Hence St John’s adding: “and so we are”. Therefore, it is not just a matter of a metaphorical title, or a legal fiction, or adoption human-style: divine filiation is an essential feature of a Christian’s life, a marvellous fact whereby God gratuitously gives men a strictly supernatural dignity, an intimacy with God whereby they are domestici Dei, “members of the household of God” (Eph 2:19). This explains the tone of amazement and joy with