The effect of being asked to do the impossibleThe nature of a propelling questionGrowing a better quality crop with less waterWhat makes propelling questions powerful?Starting to use propelling questions: the different families of constraint and ambitionSpecificity, Authority, LegitimacyWho else might ask propelling questions of us, and what happens when they do?Uber's children and the death of the trade-offThe rewards for the unreasonable challenger