This paper articulates how programme evaluation generally, and impact evaluation specifically, contributes to good governance -not by replacing politics, but by informing it. We argue that institutions with the mandate to accelerate progress in the developing world through aid transfers are particularly well suited to fund impact evaluations. We argue, in fact, that funding impact evaluations through a collective vehicle like the International Initiative for Impact Evaluation (3ie) should be a primary focus of foreign aid. Finally, we highlight the conditions needed and the additional efforts required to yield the full benefits of collective investment in finding out what works.