There is a view today in the Church that has become very popular labeled Inclusivism. As the name suggests, the driving idea behind this idea is that Christianity, and particularly salvation, includes other people from other religions. Ronald Nash, in his book, "Is Jesus the Only Savior?," explains Inclusivism this way:
Inclusivists see their position as a middle ground between exclusivism and pluralism that preserves
the most important insights of the other two views. Inclusivists agree with pluralists that God's salvation
is not restricted to the relatively few people who hear the gospel and believe in Jesus Christ. Inclusivists
agree with exclusivists that God's universally accessible salvation is nonetheless grounded on the person
of Jesus Christ and his redmptive work. (pg. 103)
So how does this work out? Well, Inclusivists depend on the "sincerity" and "commitment" one has to Faith (not to what we have faith in) as a test of whether they are to be "included." Often the idea is that if one has sincere faith and deep commitment to their god, perhaps because he/she believes it is right, or because the person never heard the Biblical Gospel, then that person is actually worshipping God by another name. Many believe that sincere Muslims, Hindus, and Jews who have deep faith in their gods will not be punished because they sincerely believed they were worshipping the true God. A famous example can be found in The Chronicles of Narnia.
At the end of "The Last Battle," as Aslan has created the new heavens and the new earth, there comes one who served Tash, the false god. Emeth, the soldier of Tash, came before Aslan, and he had "served Tash all of his days and not him [Aslan]" But Aslan bends down and this dialogue takes place;
"Son, thou art welcome. But I (Emeth) said, Alas Lord, I am no son of thine but the servant of Tash. He (Aslan) answered, Child ALL THE SERVICE THOU HAST DONE TO TASH, I ACCOUNT AS SERVICE DONE TO ME. then...I...questioned the Glorious One and said, Lord is it then true, as the Ape said, that thou and Tash are one? "
The answer that Aslan gives basically states that any true and faithful service given unto false gods cannot be accepted by them, and is only for the true God. So, despite what we think, when we do good, no matter what name we do it in, we do it for God, and evil is done for Satan, and false gods. This is an emotionally charged topic, because we obviously don't want people to go to Hell, and we want a nice and easy way to account for people who are sincerely thinking they have the right answer, but does this position reflect the Bible?
Let's look at one discussion in the New Testament. In John 3, a man comes to Jesus in the night to question Him about His teachings. It is vital that we look at who this man was. Nicodemus was a Pharisee, a "Ruler of the Jews." While that holds bad connotations to us because of the perspective we have looking back at History, we should recognize that these men were the religious leaders of their day. They took sincerity and commitment to an extreme. These were men who honestly thought they knew the truth, and as we can see from Nicodemus were sincere about their belief. So does Jesus repeat the words of Aslan here? Does he gloss over the shortcomings of Nicodemus' beliefs and praise his stolid faith, and commitment? You decide:
Truly, truly I say unto you, unless one is born again he cannot enter the kingdom of God.
and later:
"Are you the teacher of Israel and you do not understand these things?...No one has ascended into heaven except He who descended from heaven, the Son of Man. And as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up that whoever believes in Him may have eternal life."
Here is an incredibly sincere man, committed to his belief and Jesus says that Nicodemus does not understand and it is only by Christ that one is saved.
Another powerful story in the Bible that refutes this idea is found in Acts 10. This is the story of Cornelius, who was "a devout man who feared God with all his household, gave alms generously to the people, and prayed continually to God." That sounds good. If we could let anybody be "included," it would have to be Cornelius. But, that is simply not the case. An angel of God has to come to Cornelius, and tell him to send for Peter so Peter can share the Gospel of Jesus Christ with him, so he can be saved. Peter comes and shares the story of Jesus with them and the Holy Spirit works in them to salvation. The point is that they had to hear the Gospel of Jesus Christ to come to salvation.
It is not enough to believe in a god, and sincerely try and follow him. What we can glean from General Revelation about the creator is not enough for salvation. Moreover, if we try and say this, we neglect the fact that no matter how much we can learn from creation about God, we are still dead in our sins, and following the ways of the world. We are willfully and intentionally rebelling against God in our sin, though we recognize He is there, and that we are wrong for what we do. Romans 1 is clear on this, as well as Isaiah 59. We are separated from God, and there is nothing within our ability to save us, and Scripture clearly says that "there is salvation in no one else, for there is no other name under given among men by which we must be saved." Acts 4:12