Miracles and Anti-supernaturalism

[Silver]

Why is it that no one doubted Christ's existence for more than the first 1800 years?

They did. They just were not as vocal about it back then as they are now. Your statement is as absurd as those in which people claim gay people did not exist hundreds of years ago. Sure they did, but they were not out of the proverbial closet at the time.

Who says that a person has to have been written about to prove they existed?

Historians. Other people around the same time were written about, even statues were made to depict them and their existence. No such luck with Jesus, except in a fiction book. That is because he most likely did not exist as a real person.