At church one Sunday I fell into conversation about a TV programme on biblical archaeology. My friend has a deep but straightforward faith. "God is God," he said. "It doesn't have to make sense to us, we just have to believe it."

When I hear that, I want to say that it depends on what you mean by "believe". But putting it like that makes Christians like my friend assume you're going to start explaining the difficult bits of the Bible away, smoothing out the awkward bits by pretending they don't mean what they obviously do mean.

Really it's about taking the Bible on its own terms.

For instance, many chapters of the Old Testament are written in poetry. I believe them, but I don't think they are "true". When the Psalmist urges "small creatures and flying birds" to praise the Lord (148:10), we do not imagine a hedgehog singing the Doxology. Or when he says, "I have been young and now I am old, yet I have not seen the righteous forsaken or their children begging bread" (37:25) we don't, if we are wise, take that to mean that if you're a good person, you and your children will never be poor (though some prosperity preachers teach exactly that).

Instead, we wonder what "praise" means in the context of the natural world. We think about what it means to have such a rock-solid sense of God's saving and keeping power. By not saying exactly what she means, poets make us see things differently.

Other books are history, and I believe them too. But I don't have to believe them uncritically. For instance, in Joshua 8: 1-2 it says, "The Lord said to Joshua... You shall do to Ai and its king as you did to Jericho and its king" - that is, kill every man, woman and child within its walls.

But did God "say" that? Or is it a shorthand way of saying, "This is how God's people understood things at the time"? It's an important distinction. If we believe God ordered genocide and ethnic cleansing 3,000 years ago, it's easier to believe he'd do it today. If we believe that he has been slowly working his purposes out with unpromising material over many centuries, we'll bring a different perspective to stories of the past.

Another Bible genre is Apocalyptic, like Daniel and Revelation; it seems to speak of things outside our human frame of reference, and we usually think of these visions as referring to the future. There's a vast literature about the End Times, with some surprising contributors: Isaac Newton, for example, was obsessed by biblical prophecy as well as gravity.

But perhaps we should pause before getting out our calendars. It's hard to imagine that God would have given us so many chapters of the Bible which have no relevance to our lives today, and refer only to future events – and that he'd want so many of the best minds of their generation to spend months and years trying to work out exactly what they mean. It makes far more sense to ask what he is saying to us now. So Revelation, for instance, can be read as a critique of human power structures, an assertion that even the most powerful empire is under God's judgment, and a statement of the Lordship of Christ.

Do I believe the Bible? Yes, absolutely. But I also want to ask, how exactly does God want me to believe it? And there are some things it asserts as absolute statements of fact – like the virgin birth or the resurrection – and some that are obviously meant to be understood in a different way. There are other stories and statements where we aren't sure, or where Christians can legitimately have different opinions.

The danger is that "believing the Bible" becomes shorthand for "being the kind of Christian I approve of". That's not really helpful, because we might become scared of asking the sort of questions about the Bible we need to in order to understand it properly. But it's God's gift to us, and he wants us to treasure it and use it wisely.  

Follow Mark Woods on Twitter: @RevMarkWoods