Eternal sin
However, the Church further believes there is no offence, however serious, that cannot be taken away by Baptism, or absolved from in the Confessional—that no one, however wicked and guilty, may not confidently hope for forgiveness. The Catechism says that Christ desires "the gates of forgiveness should always be open to anyone who turns away from sin." As did St Augustine, the Catholic Church today teaches that only dying unrepentant for one's sins is the only unforgivable sin. Indeed, in "Dominum et vivificantem" Pope John Paul II writes "According to such an exegesis, 'blasphemy' does not properly consist in offending against the Holy Spirit in words; it consists rather in the refusal to accept the salvation which God offers to man through the Holy Spirit, working through the power of the Cross", and "If Jesus says that blasphemy against the Holy Spirit cannot be forgiven either in this life or in the next, it is because this "non-forgiveness" is linked, as to its cause, to "non-repentance," in other words to the radical refusal to be converted. This means the refusal to come to the sources of Redemption, which nevertheless remain "always" open in the economy of salvation in which the mission of the Holy Spirit is accomplished."
Adam
Christianity sees human nature as irrevocably stained by the sin of Adam. The idea is not found in Judaism (nor in Islam), and was introduced by the Apostle Paul, drawing on currents in Hellenistic Jewish thought which held that Adam's sin had introduced death and sin into the world. Sin, for Paul, was a power to which all humans are subject, but Christ's coming held out the means by which the righteous would be restored to the Paradise from which Adam's sin had banished mankind. He did not conceive of this original sin of Adam as being biologically transmitted or that later generations were to be punished for the deeds of a remote ancestor. It was Saint Augustine who took this step, locating sin itself in male semen: when Adam and Eve ate of the fruit they were ashamed and covered their genitals, identifying the place from which the first sin was passed on to all succeeding generations. Only Jesus Christ, who was not conceived by human semen, was free of the stain passed down from Adam. (Augustine's idea was based on the ancient world's ideas on biology, according to which male sperm contained the entire unborn baby, the mother's womb being no more than a nurturing chamber in which it grew.)