[BARCLAY (William)]. Treatise on the power of the pope over secular princes. Cologne : Pierre du Marteau, 1687. - In-12, stiff parchment, smooth spine, speckled edges (19th century binding). New edition of this rare work by Scottish jurist and professor of civil law William Barclay (1546?-1608). This treatise first appeared in Latin in 1609, and the first French translation was published in Pont-à-Mousson in 1611. It is a revolutionary text, in which Barclay criticizes papal absolutism and argues, in particular, for the spiritual separation of the pope from the temporal power of sovereigns, thus laying the foundations for reflection and debate on the separation of powers, which lasted for several centuries. A good copy. Some brown spots.