I’ve been asked this question many times throughout my life and before I even have a change to think my mouth say “No” but is this still the case? I spend at least two hours a day meditating and this meditation technique was taught by the Buddha 2500 years ago. Can I still say I’m not religious? While I recoiled from my initial statement I still think it’s true. I know very little about the different branches of Buddhism and the technique I’ve learned has only three secular parts that help people purify their minds. The practice of Sila, or morality, teaches me to avoid killing, stealing, lying, having sexual misconduct, and having intoxicants. The practice of Sammati, or concentration, teaches me how to concentrate my mind with the universal object of the breath. The practice of Panna, or wisdom, teaches me to purify my mind with the universal object of body sensations. None of those things make me feel religious.
So am I spiritual? My gut reaction is to say “Yes” but let me think that through also. Spirituality has become this catch all phrase that contains anyone who doesn’t want to be associated with a religion but wants to express a belief in something beyond what science can explain. As I scientist I know there are plenty of situations that science can’t explain but the open ended, create your own belief system structure that the word spirituality allows seems too broad now. I liked the emphasis on developing your own belief system based on your own experience and it was exciting that everyone had there own personal view of spirituality but I’ve been extremely humbled by this technique. I’ve discovered small bits of universal truth deep within myself that I would never have identified without this technique. My belief that everyone’s definition is just as good as the next persons dissolved and an understanding and appreciation that Buddha was light years ahead of me took its place. Instead of being driven to meet new people with new perspectives so I could continue tweaking my own beliefs, I’m motivated to sit on my cushion and use this technique to discover the truth within myself. The word “spiritual” doesn’t seem to define this practice for me.
So when someone asks me about my beliefs I simply say, “I’m a Vipassana Meditator.” While not many people understand what that means it’s the only phrase that accurately describes my practice. I can still build from the foundation that everyone’s life experiences and perspectives are different but now I believe that the new experiences that will really help me and others grow into better people with deeper understandings of truth will come from meditation. Everyone’s path is still different but the destination is the same. We will all meet at absolute universal truth in the end so I’ll do my best to respect your journey and I hope you can respect mine.
Living Vipassana 
Stephen Jay Gould talked about “non-overlapping magisteria” (i.e the “spiritual” and the “scientific”) but I disagree. Ultimately, I think, both will have to converge. This quote comes to mind: “The day science begins to study non-physical phenomena, it will make more progress in one decade than in all the previous centuries of its existence.” Nikola Tesla
Nice treatment of this very complex issue. Part of the problem of course, is that there are so many conflicting definitions of what ‘religious’ and ‘spiritual’ mean. In a broad way, this practice is both, but it is also true that the Buddha’s approach, and the approach of this tradition, is basically scientific – i.e., open to discovering what the truth is. But there’s this ‘Vipassana dogma’, too, that bugs me, a little narrowness that creeps into things, at least the way things are run. There’s one way and no questioning it. That’s pretty typical of ‘religion’. The practice itself seems to me to be outside of all that, just very pure. I agree with your approach to others’ stuff, too – people can do what they want, not anything wrong with it, just seems clear that some things are helpful and some are not. People pretty much have to discover that for themselves. That’s where my ‘belief’ comes in – I believe in the karmic path, even tho couldn’t give lots of empirical evidence for it or any agency for it. But I believe that’s why people are all over the place, all following some karmic path they have basically created for themselves, and eventually it will lead them to what’s more helpful for them… tho it may take a very long time, even lifetimes (tho not sure about that part!).
Now that’s a thought provoking quote!