A philosopher, a medical doctor, and a statistician talk about causality. They discuss the relationships between causality, chance, and statistics, resorting to examples from medicine to develop their arguments. This debate gives rise to an original trialogue, a tribute to the famous conversation between d’Alembert and Diderot, two great French thinkers of the Enlightenment. The trialogue notably offers an introduction to the philosophy of causality and an initiation to statistics, including recent developments that should prove interesting to specialists and laypeople alike.