We have to know about him in order to be able to trust him, but then there is the personal attitude of trusting him as a person and committing ourselves to follow him. There is nothing very strange about this. Trust is something we know about because it is a normal part of human life. I mean that baptism initiates us into a relationship of trust in Christ. It is often hard to say exactly when trust begins.
Little children have an implicit trust in their parents.
That is the kind of faith that Jesus taught his disciples to have in God and in himself. If a child is being brought up in a family where people do trust God, we may hope that the child will learn that trust too, and there will be no clear beginning. It will certainly be there long before it can be put into words. The time comes when it is important to say what we believe. It comes in different ways to different people at different times.