How can you possibly reconcile the justice of God with the idea that only through Christ can you be saved? Most of the world lives and dies and never even hears of Christ. There has to be some mechanism set up for all those who have ever lived to have an opportunity to hear of Christ.
The first six years of a child's life, it is like a tape recorder is on. Everything it sees, smells, touches, experiences in any way, whatever it hears, is being downloaded into the brain before the consciousness of the child is even made apparent.