The article of faith 8 puts doubts on, for the LDS, the Bible's reliability.
The Book of Mormon, if you use even scales, can be doubted, as how do you know that it was translated correctly as the original no longer exists, and is even in more trouble if in another language as if you believe Smith translated it divinely, it was only divinely translated into English.
The Pearl of great price is greatly undermined by the debacle about the Book of Abraham and it's proven inconsistencies.
And as to the D&C which to the outsider looks like a collection of sermons much like the Journal of Discourses, and why is the first sacred and the second not. Also why if it contradicts the Book of Mormon for example does it, or another address given by a President acting as a Prophet trump it. If God does not change then how can He be for polygamy and then against it, within 100 years.
