We would bring out satellite photographs and say "here's the proof."

Geography is a case in which a certain kind of proof applies. We have tested the accuracy of photographs thousands of times and they have repeatedly been shown to be correct. In other words, we know what 'proof' and 'accuracy' mean here and we have well-tested methods for achieving them. I'm not sure we are in the same position with respect to ethics. What is the 'proof' that polygamy is morally good or bad?