A religious person is a person who considers whether a fact is acceptable to his religion before he explores it. As opposed to a person who has faith, who explores first and then considers weather or not he wants to accept the ramifications.
I think faith is strong enough to be open to explore ideas that religion doesn't permit.
My point is that just because someone holds certian ideas to be "necessary" to faith, doesn't mean God agrees with their interpertation.Who gets to decide what is foundational? After all we are only human.Our best guess is probably laughable from Gods view point.
For example a person living in the southern parts of the US 200 years ago would have believed that slavery was a foundational christian belief! I believe they would have a stronger (and better) faith for questioning that "fundamental truth."
Questioning our religious beliefs and doubting our man made doctrine is a far cry from doubting God. It is perfectably acceptible, maybe even nessasary to question the thoughts, opnions, and understandings that past generations have fromed into religious doctrine.