I happen not to think that unaided reason is the only way to arrive at truth. Reason is a wonderful faculty, but you cannot use it to prove that reason is the gold standard for determining truth, since that would involve invoking a petitio that sound reasoning does not permit. I think that experience is the soundest ground for truth and there is plenty of evidence that people have had experiences of the transcendent. By that standard, the only way to know that there is life after death is to die and find out. (Of course, if your late mother walks into your room one night, I suppose you could take that as prima facie evidence.)
My own view is that the human faculty best designed for arriving at truth is the imagination, which, when soundest, tends to be grounded in experience. The problem with rationalism is that it tends to come up short on imagination. I myself have had experiences that have convinced me that if anything is true it is that there are more things in heaven and earth than are dreamt in most philosophies.