Of course, during these centuries, the gradual subjugation of the western empire by the barbarians had been powerfully operative in the obscuring of culture. Most of the public schools disappeared, and generally the light of learning was kept burning only in monasteries, and in them more and more faintly as they became more or less isolated units exposed to attack by ruthless foes or living in continual dread of such attack. Though the barbarians absorbed the old culture in various degrees of imperfection, yet the four centuries following the death of St Augustine were plunged in intellectual darkness, relieved by transitory gleams of light in Britain and by a more enduring flame in Ireland. The utmost that could be done was to preserve to some extent the heritage of the past. This, indeed, was essentially the work of men like Boethius, Cassiodorus, Isidore and Bede. Modification of Latin. During these same centuries another process had been advancing with accelerating steps. This was the modification of the Latin language. In the early centuries of Christianity literary Latin was already very different from colloquial Latin, especially in the provinces; and, as has been said, the literary output of the last age of Paganism was marked by sterility of thought and meretricious redundancy of expression. On the other hand, the writings of Christianity show a real living force seeking to find appropriate expression in new forms. Thus, with Christian writers, slavish imitation of the past gradually gave way to the evolution of a new and living Latin, which showed itself more and more regardless of classical models. To express the new ideas to which Christianity gave birth fresh words were coined, or borrowed from colloquial speech or from the Hebrew and Greek Scriptures. This Christian Latin was a real living instrument of expression, which conformed itself in its structure much more closely to the mode of thought and expression of actual life than did the artificial imitation of antiquity in which the literary productions of Paganism were clothed. It is the Latin in which St Jerome wrote the Vulgate. But with the obscuring of culture during the barbarian invasions this current Latin became more and more oblivious of even such elements of form as grammatical inflexions and concords. The Carolingian revival.