The article examines changes in teaching and practice endorsed by Vatican II. What “combination of continuity and discontinuity” (Pope Benedict XVI) shaped those reforms? Several conciliar documents set out principles guiding the changes by retrieving neglected traditions (ressourcement) and bringing the church’s life up to date (aggiornamento). The article suggests going beyond such schemes as “changing forms and permanent principles” or changes in “nonessentials but not in essentials” and instead recognizing that the council embraced reform with a view to renewing the church’s apostolic identity.