At the beginning of the nineteenth century the last remnants of Jansenism were still influencing Catholic teaching in many countries of Europe. This most insidious of heresies, preached by men of austere life and veiled by the plea of reverence for holy things, was a danger to the lax and to the scrupulous alike. It laid down as conditions for approaching the sacraments dispositions of soul which for the greater part of mankind were wholly unattainable; it presented God as the Jehovah of the Old Testament, terrible and awe-inspiring, rather than as the Christ of the New, tender and compassionate to sinners. "I tell you," said St. Vincent de Paul to one of his priests, "that this new error of Jansenism is one of the most dangerous that has ever troubled the Church."
Perhaps the most fatal effect of Jansenist teaching was that it drove the sinner from the sources of grace and the weak from the sources of spiritual strength. Frequent communion, which had been the custom in apostolic times and which had been always upheld in the teaching of the Church, was to the Jansenist a tempting of Providence. In vain did Catholic teachers explain to the people that the Council of Trent "exhorts, asks and beseeches the faithful to believe and venerate these sacred mysteries . . . with such constancy and firmness of faith . . . that they may be able frequently to receive the supersubstantial bread." Nothing, it was answered, had been laid down as to the necessary dispositions for receiving communion; and how were they to know that they had them? Theologians were divided on the subject, some teaching that very perfect dispositions were required, whilst others maintained that a state of grace and a right intention were sufficient. Another controversy had arisen as to the meaning of the term "frequent communion," some holding that weekly communion came under this heading, others that it did not. Appeals were made from time to time to Rome to decide the question, that the minds of the faithful might be at rest.
In the first encyclical of Pius X where he sets forth as the purpose of his pontificate the restoring of all things in Christ, the frequent use of the sacraments is mentioned as one of the four great means to this end. We have already seen how, when visiting his diocese as bishop, he bade the people make no preparations for his coming save attending Mass and receiving holy communion, declaring that this would be the best welcome they could give him. On the 20th of December, 1906, the Decree concerning Frequent and Daily Communion put an end to all further controversy.