Soon the study circles grew into a movement which took on the name Le Sillon after the magazine, which became their instrument.

Formulating a definition of democracy as the "social system that tends to maximise the consciousness/conscience and responsibility of everyone", the Sillon became the prototype of the YCW and other movements of specialised Catholic Action.

Cardijn always recognised his indebtedness to the Sillon as in this 1921 speech welcoming Marc Sangnier to Brussels.

In the document below, Marc Sangnier records his own impressions of his visit, citing Cardijn as "inspired by the purest spirit of 'the great times of the Sillon'".

According to Marc Sangnier, Cardijn "celebrated the work accomplished by our friends and unhesitatingly and gratefully linked his movement to ours".