“Keep the Church separate from the State – it’s best for both of them!” is complete crock. Well, at least partial crock anyway. Hear me out on this.
I actually need to do more reading, to work out the subtle distinctions between ‘religious motivation’ and ‘religious reasoning’. But in a broad sense, I see no reason to deny religious reasons in the public square – and I see some clear and relatively non-controversial examples to include them.
1) promoting compassion. Often Christians who lean left in their policy preferences will argue for things like higher taxes and greater government support of minorities. (I personally think such things need to be assessed on a case-by-case basis; I don’t have a huge ideological bias either way, just generally want to see greater government involvement well justified when it happens, but this is beside the point for now.) Let’s accept that it will best promote human flourishing to pursue a particular ‘compassionate’ policy. Such policies will often be argued for by religious people acting on their religiously-based values – and who (other than greedy selfish godless capitalists) could possibly object to that? But, if that’s okay, why aren’t we uncomfortable with the religious reasoning involved? (Note, whether the full reasoning is publicly stated or occurs only behind closed doors seems fairly irrelevant to me.)
2) preventing severe injustice. I think of the development of some prominent totalitarian state systems in the 20th century (I don’t need to name them). Unfortunately, many Christians went along with or only very weakly objected to the gross violations of human rights which were occurring. It is probable that many people were told in no uncertain terms to keep their faith out of their politics – and the world was far worse off as a result. (I’m reading Eric Metaxas’s book “Bonhoeffer”, which is causing me to ponder such things. It’ll be available to borrow soon if anyone wants.)