In your opinion what causes christians to believe in Jesus

[Sheldon]

Do you think doubt and faith are compatible?

Yes, I think doubt is integral to faith. 

Religious faith, is defined as "strong belief in the doctrines of a religion, based on spiritual conviction rather than proof."

I don't see how doubt is an integral part of strong belief? 

I don't see faith as the absence of doubt but rather doubt as the context in which faith occurs. It almost doesn't make sense to have faith in the absence of doubt.

It seems even more incongruous, to assert that a strong belief makes no sense in the absence of doubt ?

This is because faith isn't blind belief, it is trust. 

No, that's the primary definition, "complete trust or confidence in someone or something", it differs from how religious faith is defined, and this false equivalence has given us the comedy gold of religious apologists asserting "I don't have enough faith to be an atheist", as if we won't notice it is fallacious sophistry. 

And trust requires a context where you have good reasons to trust, but not enough to achieve certainty.

Give us your best reason for believing a deity exists or is possible? Only if its "spiritual conviction" I have no idea what that means or how it can be used to evidence anything, it sound purely subjective to me. 

For example, trusting a friend: you've likely already built rapport with that person and have enough evidence to take them at their word, and yet trust is always required precisely because there is always uncertainty.

Another false equivalence, I trust people based on sufficient, and sufficiently objective evidence, and my trust matches that evidence. I know of none for an extant deity, or that can demonstrate a deity / deities, or anything supernatural is even possible. Also you are using the word trust here again, but this definition of faith, using the word trust, differs from the religious definition, and again trust (for me) is evidence based, and not only do I remain dubious about theistic and deistic claims, and therefore an atheist, I have no use for religious faith, as the doctrines of religions have failed to demonstrate any objective evidence for any deity, or anything supernatural, or that they are possible.