I used to think the answer to this question was to read more theology. But the books I was reading were more about providing approved answers for those already gathered than asking searching questions of relevance to the wider world. My answer to the question below indicates that, although I love theology, I think we use its resources and insights wrongly. The letter of James makes it clear that we are not approved by God for believing the right things, but for living out what we say we believe. So, for me, thinking deeply begins, not by asking the 'what' questions, but the 'why' and 'how' ones.