As a believer I know some things. I know, for example, that Jesus is the Messiah, and that he was born, taught, suffered, died, and was resurrected to save all those from sin who would come to him.
It isn't just that I believe those things strongly. I know them. The word know is the right word. It is as appropriate as it is when I say things like "I know my wife loves me" or "I know the way from my office to my home." It is as appropriate as when I glance out my window and say to my granddaughter, "I know what kind of bird that is! It's a hummingbird."
I don't have quasi-mathematical certainty of my wife's love, the way home, or the bird's species, but I do know them. Similarly, when I say that I know that Jesus is the Messiah, I am not making a quasi-mathematical claim. Demonstrating that there is a logical possibility that I am wrong doesn't mean that I don't know. It means I don't have that kind of knowledge. But not all knowledge is of that kind. In fact, most is not. Believers ought not be cowed into giving up the word know just because their knowledge doesn't have the kind of certainty that geometric proofs have.
But neither should we give up the word believe. According to the Oxford English Dictionary the word probably originally meant "to hold estimable, valuable, pleasing, or satisfactory, to be satisfied with," to be "dear, pleasing." Perhaps that can help us understand how to continue to use it. In any case, believe is a good word, though one sometimes neglected by Mormons in favor of know.
So I know that Jesus is the Messiah and I believe that he is. Not only is it true that he is, but that he is is dear, valuable, and pleasing. To say I am a believer is not merely to report something about the truth-value I accord to certain claims about Jesus. More importantly, it is to say something about my relationship to those claims. Belief and knowledge are always matters of faith—of trust. They not only show what things there are in the world, they reveal the way in which I inhabit the world, how I share it with others.
Most important kinds of belief and knowledge require that a person inhabit the world in a certain way. Only that way of living in the world will make the knowledge possible. For example, I cannot know contemporary sub-atomic physics unless I inhabit the world of the physicist. I must learn the facts she knows and I must understand the mathematics she understands. But more than that, I must have the same dispositions that she has toward the questions of physics for those facts and equations to make sense.
That I can't know the truths of sub-atomic physics (and, believe me, I can't) without learning how to inhabit the world differently than I do doesn't mean that the claims made by contemporary physicists aren't true. I'm not arguing for the relativity of truth. But every truth makes sense only against a background knowledge and in relation to other truths, and background knowledge and networks of truth make sense only if one has the right relationships to them. Part of learning any truth requires getting into those relationships to it, as well as learning its background and the other truths with which it is related.
These complications are all the more difficult when people are engaged in interfaith discussions or when a believer is trying to explain his beliefs to a nonbeliever. Trying to explain God to an atheist requires that I try to help him at least hypothetically adopt the background knowledge and networks of truths within which we can sensibly talk about God. But to do that, I also have to decide which God I am talking about, God as Islam understands him, as Jews understand him, as traditional Christianity understands him, as Mormons understand him . . .
The complications are similar even when we aren't proselytizing, just trying to understand one another. I can give lists of things Mormons believe, but some of them may not make much sense apart from the context in which they occur. Sometimes people find it difficult to accept, even hypothetically, the background knowledge and networks of truths required to make sense of our beliefs. And vice-versa: it is an almost universal experience to think we understand someone only to discover that we don't really, or to find someone's belief utterly incomprehensible, though the person who holds the belief thinks it is almost commonsensical.
Faced with these complications, some move in the direction of believing that everyone is right, given the context and background of their beliefs: "I believe one thing, and you another; what I believe is true for me and what you believe is true for you." Choosing between desserts, there's nothing wrong with that approach to truth, but surely either there is a God or there is not, either the doctrine of the Trinity is right or it is not, either baptism is required of all or it is not, and so on. The difficulty of carrying on a discussion with mutual understanding ought not to make us give up on truth.