Looking solely to the outer form, the three stages of mediaeval thought are exemplified in the Scriptural Commentary of the later Carolingian time, in the twelfth-century _Books of Sentences_, and at last in the more organic _Summa theologiae_. With this significant evolution and change of outer form, proceeded the more substantial evolution consisting in learning, appropriating, and re-expressing the inherited material. In both cases, these three stages were necessitated by the greatness of the transmitted matter; for the intellectual energies of the mediaeval period were fully occupied with mastering the data proffered so pressingly, with presenting and re-presenting this superabundant material, and recasting it in new forms of statement, which were also expressions, or realizations, of the mediaeval genius. So the mediaeval product may be regarded as given by the past, and by the same token necessitated and controlled. But, on the other hand, each stage of intellectual progress rendered possible the next one. The first stage of learning is represented by the Carolingian period, which we have considered. It was then that the patristic material was extracted from the writings of the Fathers, and rearranged and reapplied, to meet the needs of the time. The mastery of this material had scarcely made such vital progress as to enable the men of the ninth and tenth and eleventh centuries to re-express it largely in terms of their own thinking. In the ninth century, Eriugena affords an extraordinary exception with his drastic restatement of what he had drawn from Pseudo-Dionysius and others; and at the end comes Anselm, whose genius is metaphysically constructive. But Anselm touches the coming time; and the springs of Eriugena’s genius are hidden from us.