To this mysterious atheist who (for some reason) isn't asking the questions for himself/herself....
1. "Doubt" is a cognative thing. Faith has to do with reliance/trust. I have a Ph.D. in physics and so have SOME cognative understanding of how planes fly (actually, there's a lot of unknown in this but let's move on). But is the total, absolute understanding of the physics of such necessary to board a plane? Not really.... I image most of the thousands boarding a plane today have little to no understanding at all of how planes fly, yet..... Yesterday, I had lunch at a fast food place. Did I know the food was safe? Nope.... didn't even think about it at all, actually. Did I eat the meal? Yup (enjoyed it, too.... and fortunately, I'm not sick). There is a sharp difference between what our brain "understands" and what we trust/rely/act upon.
2. Yes, religion assumes some things. But then we all do. In everything. Science itself is based on and relies on a bunch of assumptions; the whole scientific method rests on assumptions. I think this is a point that atheists evade. Can I prove I even exist? Obviously not. Can I prove any of this is real? Nope. We could all be plugged into some entertainment system in our homes on Mars. We ALL assume a LOT, things we actually can't prove. It may seem REASONABLE to us - enough so to act on it - but we can't PROVE it. Assumptions are far more common than many realize.
3. I recall in one of my undergraduate theoretical physics classes.... The prof said that what theoretical physics teaches us is that reality seems profoundly weird, FULL of things the average Joe would never even think of. Consider string theory.... IMO, in terms of where science is at now anyway, the possibility of God, Heaven, etc. seems a WHOLE LOT more possible than it would have been to the scientist 150 years ago... maybe even 50 years ago. That doesn't support that such IS "real" (even that word is a difficult in modern physics) but a whole lot weirder things seem true.... Physics is full of remarkable surprises.
4. There is a verse in Scripture, "Lord, I believe.... help my unbelief." I think every believer (in anything) can identify with that. I trust in and rely upon my wife. Do I cognatively know everything about her? Do I need to?
5. I think there is a misunderstanding among some atheists (especially the philosphical types), an assumption that religion is about answering questions. Frankly, I know of no religion that is about that or even is particularly concerned about that. Relgion is about RELATIONSHIPS, our relationship to the divine and in light of that to each other and the world around us. In my schooling, I never once found an answer to anything in the Bible - and never thought to look there. The bible is not a Answer Book, it's a series of stories about relationshiips. Even the "Creation Account" (I believe there are two of them) are not to answer how stuff got here, but is about God and us and the universe around us, stressing the RELATIONSHIPS there, stressing God as above and greater and stronger than us, passionately concerned about us, our Father. Yes, some "Native Religions" have their myths that MAY be to answer practical questions (and some see the Towel of Babel thing in Genesis as an example of that) but that's largely absent in the major world religions. Even the account of the Fall and Satan are not given in Judaism or Christianity or Islam as an "answer" to ANYTHING (and of course, it's not) but rather to insert into this account of RELATIONSHIPS that there is evil, wrong, injustice.... that's part of the reality, a part that these major religions don't skirt around but accept as a part of things, a part of relationships.
I hope that helps.
- Josiah