We study the coevolution of religion, science and politics. We first uncover, in international and U.S. data, a robust negative relationship between religiosity and patents per capita. The model then combines: (i) scientific discoveries that raise productivity but sometimes erode religious beliefs; (ii) a government that allows innovations to diffuse, or blocks them; (iii) religious institutions that can invest in doctrinal reform. Three long-term outcomes emerge. The “Western-European Secularization” regime has declining religiosity, unimpeded science, and high taxes and transfers. The “Theocratic” regime involves knowledge stagnation, unquestioned dogma, and high religious-public-goods spending. The “American” regime combines scientific progress and stable religiosity through doctrinal adaptations, with low taxes and some fiscal-legal advantages for religious activities. Rising income inequality can, however, empower a Religious-Right alliance that starts blocking belief-eroding ideas.