More than any other single thinker, William of Ockham (c.1285-1347) is responsible for the widely held modern assumption that religious and secular-political institutions should operate independently of one another. His point of departure was a tragic collision between two specifically Christian ideals: that of St. Francis and that of a society guided by the single supreme authority of the Pope. This volume begins with his personal account of his engagement in that conflict and continues with essential passages from the major works in which he attempted to resolve it.