Some say that spiritual connection or a feeling of oneness can be known through meditation. So it doesn't have to be just a belief in someone's mind but something that is tangible on a subjective level.

Some have near death experiences that touch them and change them dramatically, like brain scientist Jill Bolte Taylor who survived to tell her story.

Then there's quantum physics. The two slits experiment shows how observing (or not) the experiment affects the end result. Suggesting that there's some connection between the observer and reality. Considering that all that is physical came from the same dot of energy (ie The Big Bang) the theory that all is still interconnected on some level, is not that far fetched. After all our senses and measuring devices are only capable of interpreting a small portion of the electro-magnetic spectrum.

I'm agnostic but really enjoyed Eckhart Tolle's books. The best description of spirituality I've read after the following Einstein's quotation:

"A human being is a part of the whole called by us universe, a part limited in time and space. He experiences himself, his thoughts and feeling as something separated from the rest, a kind of optical delusion of his consciousness. This delusion is a kind of prison for us, restricting us to our personal desires and to affection for a few persons nearest to us. Our task must be to free ourselves from this prison by widening our circle of compassion to embrace all living creatures and the whole of nature in its beauty."

There you go, plenty of subject suggestions for future podcasts : )