Against the common view that miracles can attest the truth of a divine revelation Gerhard maintained that " per miracula non possunt probari oracula "; and Hopfner returns to the qualified position of Augustine when he describes them as praeter et supra naturae ordinem."
Supreme in Europe, the papacy gathered into a body of doctrine of the decisions given in virtue of its enormous de facto power, and promulgated its collected decrees and oracula to form the immutable law of the Christian world.
- C. Alexandre (Paris, 1841, 2 vols.; 1869, I vol.); Rzach (Prague, 1891; text and appendix of sources); Geffcken (Leipzig, 1902; text with full apparatus of variants, sources and parallel passages); see also his Komposition and Entstehungszeit des Oracula Sibyllina (Leipzig, 1902).