Not too long ago I had a nice discussion with Jonathan Pearce that lead to his posting about the Münchhausen trilemma.
This is an interesting thing I picked up on while debating with a (surprisingly nice) Presuppositional Apologist.
The interesting thing that came about was that once both theists and atheists come to accept the Münchhausen trilemma as the major issue in epistemology that it is, I think that secularism in terms of governance follows as a result. This post is to explain why I think that to be the case.
It should be said that if you haven't read up on the Münchhausen trilemma, follow the links above to check it out before continuing with this article.
Before I get into that, I want to point out that one doesn't have to be a presuppositional apologist to appeal to the Münchhausen trilemma. Any theist that endorses Alvin Plantinga's model of reformed epistemology and "Warranted Christian Belief" you're going to touch on Münchhausen trilemma where we start arguing about which set of axioms can count as properly basic or truly axiomatic. Generally this too ends in a stalemate.*
The interesting thing is that once the theist accepts the rationality of theistic or Christian belief by this method, they likely are going to assume that atheistic non-belief is similarly rational. This is one of the reasons I consider Randal Rauser to be a cut above his peers as an apologist since he applies this epistemology consistently and doesn't try to call atheism irrational or self defeating.
So where does secularism come into play in all this?
I think once someone has accepted that both theism and atheism are equally rational positions, I think they've necessarily boxed themselves into a position that a secular form of governance is preferred.
The reason being is that for such a person they've called the debate a draw in terms of pure rationality. This doesn't entail that they think arguments can't be used to try and persuade people, but they acknowledge that there are arguments and potential defeaters on both sides that render logical argument almost moot in terms of settling the debate.
That is to say that there is no decisive victory - it all ends up coming down to what an individual finds plausible in terms of those arguments.
Given that and the fact that we'd rather build an equitable form of government for people on both sides of the issue rather than start a civil war - it entails that neither arguments that pre-suppose theism or naturalism can really be used. This largely puts the theist at a disadvantage, since they're the ones making the primary claim. As a result of this neutrality in terms of what can be settled rationally theistic based premises can't really be used to argue for specific policies. Theists have to make their arguments from a neutral perspective.
Conversely the atheists must also assent to protect the theists right to worship so long as it did not entail impinging on the rights of others.
I think this is why we find many theists and apologists are unwilling to concede that atheism is rational.
*Note - I should say that in some cases such a theist may accept the Münchhausen trilemma but still say that atheism is irrational because of specific arguments they think make atheism internally contradictory. This is a position similar to what Alvin Plantinga holds with his Evolutionary Argument Against Naturalism. Suffice it to say such a position is very controversial given that there are many responses to that argument.