How should we handle disagreement about the fundamental nature of reality and morality? How can so many people be wrong about such important things?
One suggestion is that different people have different experiences of the divine. A Muslim experiences the divine in ways that are consistent with Islam, a buddhist in ways that are consistent with buddhism. People have different intuitions about salvation, evil, divine nature, and so on, that reflect the differences in various faiths.
But can we trust our experiences or intuitions if they lead us to different conclusions? If I build a telescope that I claim allows you to view a previously hidden facet of reality, and different people look in it and see different startling things, and some nothing, then can anyone trust the information the telescope gives them? It seems not.
Perhaps people disagree because they start from fundamentally different assumptions. We can't justify the grounds upon which we justify all else. We must assume certain axioms in order to prove anything. So a Christian might start with the Bible, or God's revelation, an atheist with reason and experience, a Mormon with the Book of Mormon, and so on. But do the fundamental axioms of different people really differ so much? Can we help believing what our senses tell us? Can we help seeing the obviousness of logical truths, such as that we should avoid contradicting ourselves? Someone might believe in a higher being not because of reason and experience, but because of a psychological or spiritual need to believe, but even then don't we share those needs? A common belief in all religions is that we all come from the same place. We all have similar starting positions.
Maybe, as fundamentalists would like to believe, some people are just smart and some are dumb, and the smart people accept their religion and the dumb people believe something else. There are fundamentalists of this kind in every religion (and of no religion), and they all have to blinker themselves to the fact that every position has had defenders that are wise, good, and often very intelligent. Often the only good answer to fundamentalism like this is experience: get fundamentalists to meet people who disagree with them, and they'll quickly learn that not everyone that disagrees with them is a fool.
Maybe then, given that there are people just as reasonable as us who disagree with us drastically and strongly, we should give up our religious beliefs. But for what? Atheism? But the problem of disagreement applies equally to atheism; for every wise atheist who thinks critically about their beliefs, there is a theist who is just as wise, just as critical, and just as rational. Even if most scientists and philosophers are atheists as polling may suggest, it only takes one rational theist to cast doubt on the claim that atheism is the only rational position. Agnosticism? No, the same problem applies to agnosticism, which is just another view about the divine (that it is unknowable) with which many disagree. Maybe the answer is that we shouldn't think about religion or faith at all. But that just isn't an option, for me at least.
Given how little we know, we should be humble. We don't understand many of the concepts we take for granted every day. The theologian St Augustine of Hippo said "If you don't ask me what time is, I know. If you ask me what time is, I don't know." The same goes for causality, free will, personhood, knowledge, etc. No wonder we can't agree on the ultimate questions.
Our religious beliefs are probably unreliable and even wrong. But that doesn't necessarily mean that we should give them up. Human knowedge advances through disagreement, and debate, and dialogue. Science thrives on disagreement and controversy, and even encourages it, which is why it's so powerful. Religion has been slow to even acknowledge differences of opinion, but I think that religious belief is also slowly moving closer to the truth. Belief in Hell and narrow conceptions of salvation are being questioned, and may even be diminishing, which for my money is a step in the right direction. But for there to be disagreements, people need to have, and hold on to, different positions. We should stay faithful to our differing faiths not for our own sakes, but for the sake of possibly furthering human knowledge as a whole.