We welcome this opportunity to acknowledge the significance of Judea Pearl’s contributions to uncertain reasoning and in particular to his work on causality. In the decision analysis community causality had long been “taboo” even though it provides a natural framework to communicate with decision makers and experts [Shachter and Heckerman 1986]. Ironically, while many of the concepts and methods of causal reasoning are foundational to decision analysis, scholars went to great lengths to avoid causal terminology in their work. Judea Pearl’s work is helping to break this barrier, allowing the exploration of some fundamental principles. We were inspired by his work to understand exactly what assumptions are being made in his causal models, and we would like to think that our subsequent insights have contributed to his and others’ work as well.