It really takes a lot of faith to take someone at their word unless you really know them well. Yes, people are fallible, but God is not. He promised Abraham what seemed like the impossible. But he knew God and contrary to hope, in hope he believed.
There are many, including myself that have never got the opportunity to touch Jesus and to confirm the scars and wounds, yet we have seen Him. Not His physical being, but His handiwork all around us.