For me the main thing I can hang my hat on for certain is the gospel which is Jesus as revealed in scripture, God’s written word. By faith we know, a knowledge or assurance dependent on faith, yet in the case of scripture and specifically Jesus’ resurrection, not devoid of evidence. That is not to say that I don’t accept some things as true, like gravity. The question may end up being not only how much weight we put on something, but more importantly, why and what kind. We might find that the difference ends up being whether or not we trust a person, God (who, to bring in something complex, and well beyond us is one God in three Persons).
But on many things people seem to hold tenaciously to as matters of first importance, it often seems to me that it’s more complicated than that. That is one reason I like science, even though I really am not gifted in that field. Science keeps asking questions and is open to new answers, new ways of seeing things. Good theology should be like that. Some things have been well established by the church from scripture. Of course when you’re talking about God and humanity along with real life, we can begin to understand that while the Bible is wisely straightforward to the point of simplicity about some things (like the reality of good and evil, light and darkness), we also come to understand that there is much that we don’t know. So that we had best withhold judgment on a good number of matters.
And even what we do know is completely dependent on something beyond us, beyond our senses. Otherwise we could never know anything. That something is a Someone: God. We can rest assured in what knowledge we have, while at the same time seeing the entire enterprise as interactive, so that much of what we do know is relational and life-oriented. In other words a good part of knowledge from God found in scripture and mediated through Christ in the church is knowledge for life in this world in terms of love and how we are to live. It is rooted in history and for the real world.
Humility is the order of the day on this. We need to keep asking questions. But above all, to trust the God who has given us his word in scripture and in his final Word, Jesus.