Totus Tuus was Pope John Paul II's apostolic motto. It is a Latin phrase meaning "totally yours" and expressed his strong Marian devotion and his respect for Saint Louis de Montfort and the Mariology in his works. The former pontiff explained the meaning further in his book Crossing the Threshold of Hope where he defines it as not only an expression of piety, or simply an expression of devotion and that it is deeply rooted in the Mystery of the Blessed Trinity.