The early 20th century had many challenges leading up to World War I. both in the world and in the Church, and St. Pius X sought to confront them.
One of the most enduring of his legacies was to encourage frequent holy communion.
He wrote in his decree Quam Singulari that everyone should receive holy communion more often, even daily if possible.
At the time, Catholics were accustomed to receiving holy communion only once a year. Very few would receive holy communion on a weekly basis, and typically only priests would receive on a daily basis. St. Pius X wished to correct this practice of abstaining.
St. Pius X used that same decree to lower the age of First Communion to the "age of reason," which typically is around seven years old, from the usual age of about 12 at the time.
Motto
Pope Benedict XVI reflected on St. Pius X's legacy in a general audience in 2010, first pointing out how his motto shaped his pontificate:
Pius X's Pontificate left an indelible mark on the Church's history and was distinguished by a considerable effort for reform that is summed up in his motto: Instaurare Omnia in Christo, "To renew all things in Christ." Indeed, his interventions involved various ecclesiastical contexts.
He worked to reform such things as the Roman Curia, Code of Canon Law, the liturgy, and more active participation in the sacraments:
St. Pius X also "intervened decisively, condemning 'Modernism' to protect the faithful from erroneous concepts and to foster a scientific examination of the Revelation consonant with the Tradition of the Church."
In all of these reforms, according to Pope Benedict XVI, St. Pius X focused on Jesus Christ:
St Pius X teaches all of us that at the root of our apostolic action in the various fields in which we work there must always be close personal union with Christ, to cultivate and to develop, day after day. This is the essence of all his teaching, of all his pastoral commitment. Only if we are in love with the Lord shall we be able to bring people to God and open them to his merciful love and thereby open the world to God's mercy.
His example should inspire us today in every reform, first focusing on a "close personal union with Christ." If we are able to establish that union, everything else will fall into place.
