This is the theory that country that emerges into modernity will secularise, and turn away from religion. It remained largely un challenged until the 1980's.
In the modern world some key themes that made secularisation happen:
Knowledge: appeal to reason and control over nature, and autonomy of the individual is basis for final knowledge. Scientific: world discovered not mediated Industrial: new social classes, fragmented urban living, diversity Democratic: decentralised, toppled hierarchies, participation etc.
We see the church resisting modernity, then embracing it, along with the rise of the Nation Sate. Eventually in it's response, the church had accommodated to modernity.
Yet here were are today in a world that is far from secularized, with a high percentage of people still connected to organized religion or other forms of spirituality.
But largely in the UK people have delegated functions to churches â€“ of marking life cycles, moments of national significance, times of tragedy etc.
Modern societies corrode collective memory, we are an amnesiac society in the UK. Maybe the church has a role for vicarious memory and for providing an understanding of the future from the memory we have.
And as we emerge into a post scientific, post-industrial, post nation state world, the post-secular is growing.