This question has come up from several people reading the Dave Riggler stories. In one sense, it has an easy answer: Culturally, Dave comes from a Catholic family. In another sense, though, it’s not so simple. If you’ve read any of the Dave Riggler stories, you recognize that Dave isn’t a practicing Catholic, even in a casual sense. It also depends on what leg of Dave’s journey you meet him on. The Dave Riggler in “First Steps” is not the same person, emotionally, as you’ll read about in “The Fight” or “Confirmed”. And none of these is the same, spiritually, as the person you’ll meet in “And Ye Shall Be Healed”.
In terms of how we see the world today, I would call Dave’s attitude in later stories atheistic, but not in the Richard Dawkins tradition. He doesn’t have that kind of certainty. He seems open — even hopeful — that his belief is incorrect. And his spirituality centers more around people he knows than it does spiritual leaders (a term I use broadly to encompass most modern religions).
If you really want to know what Dave’s spiritual beliefs are all about, “And Ye Shall Be Healed” is probably going to be your best indication. At least, until he evolves in later stories. 🙂