Gavra and Sam (and maybe DY but I think he already agrees with this):
Let’s use mashiach as a simple example. If you agree that there is no way to determine the objective reality of whether there will be a Mashiach (and assuming there was no nevuah or unanimous tradition) how would you believe that Mishiach will come. If you acknowledge that there is a deiah that there won’t be mashiach, and you acknowledge that there is no way to determine the reality then the best you can do is to think Mashiach will come or to be more noteh that he will come, but you can’t absolutely believe it.