And for faith.. Can’t you believe in anything using faith?
Faith, Belief, Knowledge, having a Hunch, and Speculation are not distinct concepts, but rather, differing degrees of the same concept. We accept a thing as truth — call it X — on the basis of some other thing — call it Y — also being true and being at least somewhat indicative of X. How indicative does Y have to be on X? Well, that depends. If you are shooting for a Speculation, then not really very indicative at all; if a Hunch, then slightly indicative; if Faith, moderately indicative; if Belief, very indicative; if Knowledge, completely indicative. Think of these terms according to a sliding scale, not as distinct processes.
So then, we use “faith” in one of these ways every day. The classic though flawed example is that we daily sit in chairs even though — technically… — we have little reason to believe that that specific chair will hold us up this particular time.
Scientists, then, use faith all the time. Not in their science itself, as such; but nonetheless that all scientists depend upon a set of unfalsifiable beliefs. These beliefs are equally as questionable as the theist’s beliefs. Philosophers tend to call these “metaphysics” as a catch-all term, but others have come up with more clever terms like “worldview” or the “spectacles” through which one views the world. A person’s basic core beliefs in metaphysics cannot be disproved using the scientific method, which according to nearly all atheists is the way to prove everything. This sounds familiar… oh yeah.
So, the question is not “should we use faith to believe X,” but instead, “do we have a strong enough Y to not be exercising BLIND faith in X.” The answer to that question for Christianity, I am convinced, is yes. We may never fully establish the claims of Christianity beyond the faith level — as in, the arguments for Christianity may never become deductive, they may always retain some amount of slippery inductive flexibility. But even still, this retains the ability to reasonably believe without mere speculation or hunch holding.