One place to start might be the historical witness
Hmm. Maybe an analogy or two… because our reason is good and we
should use it – to decide whether to – with our eyes open, not blindly – actually trust a person.
Analogy 1: Your mother has never lied to you about anything you’ve double checked before. When she told you dinner was on the table – it was. When she told you she’d stay up all night helping you finish your big project – she did. When she told you she’d pick you up after school – she always did. Now suppose one day she tells you that she had lunch that day at a local restaurant with her friend Betty, and you say:
“Whoa whoa whoa. Let me stop you right there. I wasn’t there so I can’t check this one. Show me the receipt from the restaurant, and you’d better have taken a picture of you with Betty together, or I can’t reasonably believe this happened. Your word isn’t good enough; I need absolute proof.” Wouldn’t you see there’s something wrong with that? That if your mother has never lied to you before, it’s actually contrary to reason to disbelieve her about an event just because you don’t have
absolute proof beyond her word? That when a person has proved themselves trustworthy on things we can check, it’s reasonable to trust them beyond that as well?
Analogy 2 (because there actually is lots of great historical evidence for Christianity, and I’d encourage you to seek it out! The Catholic Answers store should have great books available, and they offer so much content free online): Even after we’ve seen good evidence, trust is often required before an action. We can see the parachute get packed, we can know that it was packed well – but there’s still a moment when we have to choose to trust it and actually leap out of the airplane.