… is from page 569 of the 1988 collection of Lord Acton’s writings and notes to himself (edited by the late J. Rufus Fears), Essays in Religion, Politics, and Morality; specifically, it’s an undated note drawn from Acton’s extensive papers at Cambridge University:
Institutions and laws have their roots not in the ingenuity of statesmen, but as much as possible in the opinion of the people.
