50 The purpose of this exhortation of Ours is not to lend substance to the belief that perfection consists in rigidly adhering to the methods adopted by the Church in the past and refusing to countenance the practical measures commonly thought to be in accord with the character of our time. These measures can be put to the test. We cannot forget Pope John XXIII's word aggiornamento which We have adopted as expressing the aim and object of Our own pontificate. Besides ratifying it and confirming it as the guiding principle of the Ecumenical Council, We want to bring it to the notice of the whole Church. It should prove a stimulus to the Church to increase its ever growing vitality and its ability to take stock of itself and give careful consideration to the signs of the times, always and everywhere "proving all things and holding fast that which is good" (33) with the enthusiasm of youth.
Source: Ecclesiam Suam (Vatican.va)