Assertion (A): The assertion is valid. A significant shift in Western social history involved the disjunction of religious and political authority, departing from a singular system where both held sway over the populace.
Reason (R): The reason accurately depicts secularization, characterized by the separation of religion from the state and its reclassification as a private domain. Previously, religious adherence was a civic obligation, which evolved into a matter of personal volition, adopted by individuals and groups.
Connection: The reason's description of secularization directly corresponds to the assertion's point about the separation of religious and political authority, thus validating the reason's explanatory power for the assertion.