1.) On the one hand, we want religion to be a genus containing both theist and non-theist doctrines, that is, religion as such must be about something more general than service or devotion to the divine. This means religion has to be about “the transcendent” or “the mysterious” or about “higher powers” (though not necessarily gods). On the other hand, we do not tend to see politics, sports fanaticism, science, school spirit, etc. as religious acts, even though all of these things invoke transcendent, mysterious feelings in those who love them.
2.) Religion is seen as both essentially private and yet also as having definite opinions about what is just, that is, about things that find their full expression in the public sphere. This means that religious persons are, by their very beliefs, forced into a sphere where their motives for action are necessarily viewed as suspect. Religious persons are required to give irreligious reasons for anything they want to see done in the public sphere even though everyone (including their friends) has good reason to assume that these are not their real motives. This is balanced against the odd paradox that the nominally or ceremonially religious (as opposed to the irreligious or the fervent) often seem to do best in the public sphere.
3.) Thesis: We should base our public appeals on rational reasons and not religious ones since reason is common to all persons and is publicly verifiable whereas religion is not.
3a.) It would be better to say that just as reason is common to all, though it can be in greater and lesser states of health or corruption, so too religion is common to all in the same way. There is no reason to assume man is fundamentally rational in a sense that is not essentially religious. Our evidence that human being are religious (atheists notwithstanding) is about as good as our evidence that man is an omnivore (vegetarians notwithstanding).
3b.) If by “reason” we mean (at least as a paradigm) “science”, then it is simply not true that reason is common to all persons. Our scientific rational paradigm is characteristic of a minority people, whether we consider all persons now living or all that have lived throughout history. If we shift from speaking of science as actually accepted to science as an ideal, then an apples to apples comparison would have to consider religion in its ideal state as well.