What are the differences between Protestantism and Catholicism?
The main difference between Protestantism and Catholicism is in the manner of salvation. The Catholic church says that to be saved one must receive Christ and in addition to this perform good works. The Protestant churches believe that the only means to salvation is the reception of Christ in one’s heart. Salvation is the free gift of God (sometimes called Grace). One cannot earn the gift.
The main differences between Catholicism (Roman) and other Christian denominations are based both in doctrine and structure. The Catholic Church is the oldest Christian religion, St. Peter the first Pope. As the Church grew more structured and hierarchical in the first several centuries after Christ (AD), all doctrinal authority (although challenged by several schisms) came to be located in the Vatican and the popes regarded as infallible. The early Catholic Church allowed priests to be married; this changed in the so called Dark Ages because of disputes over property and inheritance rights. Many people may be surprised to learn that the only ex cathedra (i.e., from the chair) teachings that can never be changed are doctrinal, and have nothing to do with such contemporary issues such as birth control, abortion, and homosexuality. The Catholic Church especially venerates Mary (as opposed to "worshipping" her) and allows, through a process of beatification, for the constitution of saints, many viewed as patrons of such matters as animals (St. Francis of Assusi), lost causes (St. Jude), and childbirth (St. Margaret). Catholics may pray to God or Christ through intercessors such as Mary and the saints. Other major doctrinal differences between Catholic and Protestant belief include Catholics’ belief in the doctrine of transubstantiation (that is, that through the power of the priest and the Mass, the communion wafer does literally become the body of Christ); and the notion of justification (salvation) by good works, including but not limited to taking of the Sacraments, whereas Luther and Calvin, sixteenth century originators of the Protestant Reformation, held that the doctrine of transubstantiation was too akin to "magic" and that salvation, regardless of one’s good deeds, was solely dependent on God’s grace. The Catholic Church has a longstanding intellectual tradition, beginning with primarily St. Augustine and St. Thomas Aquinas; of the various Catholic religious orders, the Jesuits (founded in the sixteenth century by St. Ignatius Loyola) are particarly associated with many fine institutes of higher learning worldwide. Today’s Catholic Church is often identified with its arch-conservative positions on priestly celibacy and matters of sexuality and reproduction, but the Church’s vital left wing, including the "liberation theologians," strongly advocates for social justice, care for the poor, the immorality of most wars, and the inequalities born of capitalism.