1) Ecclesiology is the study of the Church. The Church was founded by Jesus Christ and is the congregation of baptized Christians under the authority of the Pope. 2) The Church has four identifying marks - it is one, holy, catholic, and apostolic. It preaches one common faith and doctrine throughout the world. 3) Membership in the Church is necessary for salvation, though those who are unaware of the Church through no fault of their own can be saved if they love God and try to do his will. Outside the Church there is no salvation.