From Motu Proprio, Summorum Pontificum

The Pope stressed: "There is no contradiction between the two editions of the Roman Missal. In the history of the liturgy there is growth and progress, but no rupture. What earlier generations held as sacred, remains sacred and great for us too, and it cannot be all of a sudden entirely forbidden or even considered harmful. It behooves all of us to preserve the riches which have developed in the Church’s faith and prayer, and to give them their proper place."