Bavinck: Alien Salvation

All religions seek a way of salvation; all human beings long for happiness because the human heart is created for God. Unique to the Christian religion is the reality of Jesus Christ and the redemption he brings as fully God's initiative; all other religions seek redemption through human action. However the human problem is conceived, it remains human beings who must satisfy the deity and fulfill its demands or law. All religions or philosophies other than the Christian faith are autosoteric.

The biblical viewpoint is radically different; salvation is solely a gift of grace.

--Herman Bavinck, Reformed Dogmatics, 3:485