When religion and politics travel in the same cart, the riders believe nothing can stand in their way. Their movements become headlong — faster and faster and faster. They put aside all thoughts of obstacles and forget the precipice does not show itself to the man in a blind rush until it’s too late.
Frank Herbert (1920-1986) American writer
Dune, Book 3 “The Prophet” (1965)
(Source)
Jessica, quoting a Bene Gesserit proverb.
In Appendix 2, there is reference to another Bene Gesserit teaching: "When religion and politics ride the same cart, when that cart is driven by a living holy man (baraka), nothing can stand in their path."