http://www.youtube.com/watch?v=MHsB3RviFN4
In this video, philosopher and ethnobotonist, Terence McKenna discusses the relationship between individual consciousness and cultural systems with a simple and approachable vocabulary.  He advises us to keep the self as “the final arbiter” in a way not unlike the Buddha in the Anguttara Nikaya when he instructs the Kalamas of Kesaputta not to rely on “oral tradition, lineage of teaching, collections of texts…” but rather to “know for yourselves”.
DIY fo life yo.
If McKenna wets your whistle …
… I’d strongly recommend checking out this video below where he talks about shamans as “tech support” for our cultural and personal “operating systems”, and psilocybin mushrooms as tools to “clear space” on our individual hard drives. The Tech/ Spirituality crossover here really gets me going, but most importantly I think it presents spirituality in a very scientific framework, which may be helpful to explain it to some of your science minded friends.  Enjoy!