testname123's comments

This assumes that there is indeed no difference between fact and fiction. However, facts need to be consistent among themselves. In such a case where a fact can be disproved by a lack of consistency with directly observable phenomema, no appeal to trust is required. For eg. the earth is not flat, etc.

While not applicable for all claims, some can be verified by consistency. For example, claims a and b cannot both be true if a is inconsistent with b, and this hold regardless of who claims a or b.