"The bonds which bind men to the Church
in a visible way are
   profession of faith,
   the sacraments, and
   ecclesiastical government and communion.
He is not saved, however, who,
   though part of the body of the Church,
      does not persevere in charity.
   He remains indeed in the bosom of the Church,
      but, as it were, only in a 'bodily' manner
      and not 'in his heart.'
All the Church's children should remember
   that their exalted status is to be attributed
      not to their own merits
   but to the special grace of Christ.
If they fail moreover to respond to that grace
   in thought, word and deed,
      not only shall they not be saved
   but they will be the more severely judged."

Second Vatican Ecumenical Council,
Dogmatic Constitution on the Church, 14.