Was it modern atheists?
Well where did the concept of sacred and secular come from?
Perhaps from Jesus who said
“So give back to Caesar what is Caesar’s, and to God what is God’s.”
The idea of the secular was arguably also developed and promoted by more by Luther with his notion of "two kingdoms" and by Augustine in The City of God.
These thoughts and observations were prompted by attending some of a seminar series last year at the Centre for History of European Discourses at UQ. I wished I had got around to blogging about those I attended.
I am looking forward to the next series, Narratives of Secularisation which begins tomorrow with Peter Harrison speaking on "Science and Secularisation."