Have you also encountered “faith” set in contrast to “reason”? The proponents of such a view don’t agree among themselves as to what is the sequel. Some will claim that only reason is trustworthy. Others say that only faith is trustworthy. A third group will say that both faith and reason have their peculiar value, but when all is said and done, either one or the other must dominate.
The fact is that to set faith and reason in opposition is to propose a false disjunction, as if it has to be one or the other. Furthermore, faith and reason have different purposes and results, and to set them in opposition is to make a categorical error. To say it more colloquially, to compare and contrast faith and reason is like comparing and contrasting apples and oranges rather than putting them both into a fruit salad.
The issue is not reason versus faith. Rather, the issue is that we are always working with limited evidence. Permit me explain it this way.
When I know that a particular person has certain abilities (I have evidence to that effect) as well as the appropriate disposition, I have reason to trust that person to do something for me related to that ability. It could be said that I have faith in that person, but in fact, my faith is more focused than that. It is faith related to a peculiar ability and disposition.
What I don’t know about the person (and I don’t know everything about anyone, not even myself) keeps me from asking the person to do something for me in that particular area which for me is unknown. Perhaps the person is able to fix my furnace, but I am not aware of that ability. Perhaps the person is willing to fix other people’s furnaces, but I am not aware of that disposition. Not knowing those two things (a matter of knowledge), I will not trustingly ask (a matter of trust / faith) that neighbor to fix it.
My faith in people only extends to what I know about them. If my neighbor tells me one day, “I can fix your furnace”, I will decide whether to trust him to do so on the basis of his previous track record in other areas. That is a reasonable way, and the common way, of doing things.
So, trusting someone to do something on the basis of self-made claims is reasonable if that person has shown adequate evidence of being a trustworthy person. If I have no reason to trust him, yet still do trust him, that would be unreasonable behavior on my part. It might turn out well. It might turn out to be a disaster. I have no reason to blame anyone but myself in the case of the latter.
Where does that leave us? We are left with the matter being one of evidence. Do I have evidence that the other person has both the ability and the disposition to warrant my petition for help? That evidence will establish the trustworthiness of my act of faith in that person.
Faith without evidence provided by knowledge is a crap shoot. Knowledge without faith is a furnace that is still broken.