The basic principle of the True Devotion is to go to Jesus through Mary just as Jesus comes to us through Mary. The aim of the Legion therefore is to bring Mary to the world as the infallible means of winning the world to Jesus.

This presupposes a proper understanding of the God given role of Mary in the plan and execution of the work of redemption. Following on those principles Frank Duff passionately believed that real devotion to Mary obliges us to apostleship.

An important way of understanding the nature of all apostolate is by seeing it as a sharing in Mary’s maternal care of the mystical Body of Christ and indeed of all humankind.