St. Paul of Tarsus, who became an apostle after the death of Jesus contributed largely to the development of Christianity as a world religion. He laid the foundations of Christian theology. Believing in the need for non-Jews to be converted to Christianity, he travelled widely to spread the gospel, to establish new churches and to strengthen them. On his journeys he was sometimes forced to flee, sometimes arrested and imprisoned. During this time he wrote his Epistles (letters), the earliest Christian texts. More than half of the Book of the Acts of the Apostles deals with the activities of St. Paul. According to him the First Adam brought sin and death into the world, while Jesus, the Second Adam, brings life. Mankind, when at one with Jesus, can, like Him, be reborn and gain the power to overcome death. In his First Epistle to the Corinthians, St. Paul stated that the three Christian virtues are faith, hope and love, and the greatest of these is love. The essence of religions, he maintains, is not to conform to the decrees and prohibitions as envisaged in the Old Covenant between God and the Children of Israel, but rather to share Christ’s love of God and His suffering, and to join in the New Covenant which was made real with the redeeming sacrifice offered to God in the name of all mankind. Jesus did not discard the decrees laid down in the Old Testament, but He relieved mankind from the yoke of ancient laws by making peace with God through His own sacrifice. The dominant authority was no longer the prohibitions and decrees of ancient law, but that of love. St. Paul was beheaded in Rome, probably in 67. What he did to Christianity long-term was to make Christ central to the new religion, just as the Law had been central to the old.
Women play an important role in Christianity. The Virgin Mary holds a prominent place in the religion and is one who is awarded the greatest respect. Gratitude to Mother Mary is expressed in prayers, especially in the Roman Catholic Church. Jesus was cared for by a number of women throughout His life and they remained loyal to Him even at His crucifixion. When He had risen from the dead, He appeared first to Mary Magdalene and to Mary, mother of James.
Christianity requires that believers and converts should worship God alone, and this monotheism brought them into conflict with the Roman State since Rome regarded loyalty to its own religion and the cult of emperors as the duty of every citizen. To deviate from the formal religion was considered a political crime, though with polytheistic faiths it is possible to be involved in several religions at one time. For this reason Christianity was mercilessly suppressed for a long time -250 years- and believers suffered terrible tortures and prosecutions. The Decree of Milan (in 313) granted Christians the same rights as the adherents of polytheism, and Christianity was declared the state religion in 392 by Constantine the Great. He was the first Roman Emperor to be converted to Christianity, thus creating a governing class of Christians, gaining a privileged position for this religion. He was a pioneer in the conversion of the Roman Empire to Christianity and is regarded as a saint in the Orthodox Church.