Someone read one of my sermons and asked the following question:
Does a person have to "understand" the Trinity to be saved? What if they believe in God the Father and Jesus as his son, but can't really grasp the whole "One God in three persons" thing?
I think the answer goes like this. You don't have to understand the Trinity in order to be saved. If that were required, then very few would be saved. If a person, having studied the issue, came to the conclusion that the Trinity could not possibly be true, they would be in the position of a Muslim who says, "God can't have a son." Such a person might admire Jesus but would never look to him for salvation.
When we were in Nazareth on our recent Holy Land tour, we drove past the Catholic Church in the heart of the city. Our guide pointed out a banner placed in front of the church by some Muslims. The banner quoted a verse from the Qur 'an to the effect that God does not have a son and could not have a son. That illustrates my point. If Jesus is not God's Son, if he's only a prophet or a holy man but not the Son of God, then he's not able to save anyone.
It is enough for a lost person to say, "I believe Jesus is the Son of God who died for me and rose again." That's the basis of true, saving faith.
For more on this topic, read The Mysterious Doctrine of the Trinity.