Through the middle ground of theology.
Theology is perhaps the oldest form of rigorous thought. It takes spiritual thought and molds it into a form that can be shared throughout a society. All ancient societies had theology, as theology is what happens when you take people’s individual spiritual thoughts and beliefs and share them with each other and eventually form a core set of understandings.
Theology and philosophy share a lot more than you would expect. If you compare and contrast philosophy with even more rigorous forms of thought, such as mathematics or science, it can be seen how the rational mind might rebel at the seeming uselessness of the discipline. But the reality is that unrigorous forms of thought gradually ‘spawn’ off more ‘useful’ forms. Theology eventually created philosophy, philosophy created epistemology, epistemology created science. Theology is closer to philosophy than philosophy is closer to science.
Theology and philosophy both share an obsession with ‘absolutes’, that the sciences and humanities lack. Theology seeks to turn belief directly into truth. Philosophy is interested in pure wisdom, what you get when you try to isolate understanding from religion. Other academic disciplines labor under the need for a shared set of justification rules. Philosophy, on the other hand, can accept input from religious or theological sources. It’s only interested in answering questions. Novel arguments can come from anywhere.
Not convinced yet as to the value of religious input into philosophy? Well consider moral philosophy, where philosophers have been grappling since ancient Greece over what the ‘right’ way to conduct yourself is. Religion contributes as much to the debate as humanist thinkers. Religion, and religious thinkers, are almost entirely obsessed with the quest to create ideological frames, frames that both the smartest and the most disadvantaged of us can agree with.
Anybody with a particularly strong spirituality can contribute to this marketplace of ideas. Your spirituality will create strong beliefs, that will conflict and contrast with the society of the day. If they’re strong and relevant, you can gain notoriety for them. Religious leaders will take those thoughts and work them into their sermons. Religious thinkers will sense the shift in popular belief, and work those shifts into their theology. There’s a thriving dialogue between theologians and philosophers. Some branches of philosophy deal more with the scientific side, others deal more with the humanistic side.
As with anything humans do, there are layers upon layers upon layers of separation of concerns. But that doesn’t mean you can’t connect the dots yourself.