Start with something non-religious. Think of these medical dramas which show even the time of my own childhood, the documentaries which show doctors as white-coated invincibles, the patients as wide-eyed innocents ready to believe that all will be well as they descend into what Robert Frost called "the dark of ether". Nowadays fully-fledged hypochondriacs like me can look up procedures, statistics, symptoms, photos (God preserve us from the photos) and learn doubt. We realise when we are being soothed, and the best that can happen is that when we're actually in extremis we feel soothed. It's when normality returns that the doubt arrives.
And I think it's much the same with religion. All the old certainties - from hell to heaven and places in between - are now subject to the scrutiny of science and knowledge. We know what's up there, out there, beyond ... it's not a mystery any more. We can no longer feel sure that God's in his (note - his) heaven, which is up there in the sky. I remember wrestling at University with the teleological and ontological proofs of the existence of God, at a time when I didn't believe in anything. It was a struggle, but not a spiritual one. It changed nothing; it was easier than Formal Logic; I passed the exam.
All this conspires to make me increasingly irritated at people who assume that if you adhere to a faith you are either "throwing reason out of the window" (what my father said when I announced I was going to be confirmed at the age of 28) or are somehow sufficiently ill-informed to accept a child's version of religion. (I also become irritated at Christians who insist that that's the only way, but that's another story). Someone who thinks and challenges and argues is going to bring that attitude to what they call God - and if having done so they can find themselves happy with the language and attitudes of a faith system, that is where they will exercise their minds as well as their souls.
God - that word we use to describe the indescribable, remember? - God hasn't shrunk because we know the workings of the world that we used to consider a sacred mystery. God isn't the little shrivelled creature of some celebrated fiction. My understanding of this word, this concept, is of something at once all-encompassing and omnipresent and at the same time tiny enough to be within every mind that allows itself to wonder, every heart that allows itself to melt. God is in every moment of thankfulness; still there when the heart hardens and shuts God out.
When a faith-structure allows for this kind of vision, provides the framework of beauty and wonder and loss of the self-consciousness that inhibits, gives space for sorrow and joy and the tears of both, that is what I call Church. When I find myself in it, I am grateful. When it is threatened - and it can so easily be threatened - it is like an impending death. When it solidifies into something else, I'm better off without it, sad though that feels.
But try explaining that over the dinner-table. Or on a bus.