The article discusses the causes of the subprime crisis and how to improve regulation. Different ways of looking at finance, called paradigms, influence how we understand the crisis. The agency paradigm, which focuses on individual actions, is popular but may not be the whole story. Other important factors include collective welfare failures (like externalities) and collective cognition failures (like mood swings). To fix regulation, we need to consider all three paradigms together, even though they sometimes suggest different solutions.