When a person believes in something they cannot see or prove, they are often saying this is what I want to believe in, this is what I would hope is true. Even atheists put faith in what they cannot see and believe it to be true for the same reason. For example, they hope creation came from a random explosion without need for a God. They were not present at the dawn of creation to confirm this, neither can they demonstrate this to be true today. Since they would like it to be true, they believe in it, and this is why they use their time, intelligence and money to attempt to prove this to be true. If they preferred to believe in a world view in which God was in control, they would not do this.