The whole purpose of creation is that God would form a bride from humanity, so that He could bring that bride into the triune communion as the bride of His eternal Son. That’s the goal and the destiny of all creation. That’s pretty practical by itself, but Jesus is praying for His disciples and for the unity of His disciples. And He not only prays that the disciples would be one with the Father and the Son—that the Father and the Son would make room in their own communion for us—but He also prays