many verses in the Bible support an exclusivist view of Christianity:
John 14:6 - "i am the way and truth and life. no one comes to the Father except through me" (Jesus)
Acts 4:12 - "salvation is found in no one else, for there is no other name under heaven given to mankind by which we must be saved"
taken at face value, John 14:6 suggests that salvation depends on absolute + explicit commitments to Jesus. some exclusivists make exceptions:
children who die before they are able to make this commitment can be saved - this is also reflected in the reason that used to be given for the practice of emergency baptisms
those who die never having heard about Jesus - will be judged on the conformity of their lives with NML
fundamentalists adopt a narrower interpretation of John 14:6
salvation depends on declared belief in Christ which means evangelism is an absolute priority
the belief in God was uniquely revealed in Christ is seen as a central truth of Christianity, which is threatened by any dilution of exclusivism
before Vatican II, the official view of the Catholic Church was that there is no salvation outside the Church
however, Vatican II emphasised the importance of dialogue with other religions, seeking to foster mutual understanding + respect for different faiths: "what unites us is much greater than what divides us"
modern Popes such as Pope Francis, advocate for a more inclusivist view of other religions: "every religion is a way to God"