Randomized controlled trials (RCTs) are supposed to be the gold standard for testing causal claims, especially in evidence-based policy and medicine. But there are a great many kinds of interventions that do not lend themselves to testing by RCTs, like talking psychotherapies. This seminar will look at single-case studies as an alternative. What would it take in order for a series of single-case studies to provide as much evidence as an RCT about the same kind of claim that RCTs can provide evidence about?