Question

Please help! British Literature ,Essay due soon .W.B. Yeats Question, Help?
I am doing a report and I came across this quote "Yeats said that societies don't collapse on their own; there must be outside pressures as well as internal conflict before they collapse." on the internet. I do not want to quote it or use it if it isn't true. I can't seem to find out where yeats said this or if it is from a poem? I am not a poetry expert by far, but I thought it may be in the context of "The second coming" Can anyone tell me where this is from