The introduction of the Breton romances into the current of European literature worked a not less profound revolution in the manner of conceiving and employing the marvellous. In the Carlovingian poems the marvellous is timid, and conforms to the Christian faith; the supernatural is produced directly by God or his envoys. Among the Cymry, on the contrary, the principle of the marvel is in nature herself, in her hidden forces, in her inexhaustible fecundity. There is a mysterious swan, a prophetic bird, a suddenly appearing hand, a giant, a black tyrant, a magic mist, a dragon, a cry that causes the hearer to die of terror, an object with extraordinary properties. There is no trace of the monotheistic conception, in which the marvellous is only a miracle, a derogation of eternal laws. Nor are there any of those personifications of the life of nature which form the essential part of the Greek and Indian mythologies. Here we have perfect naturalism, an unlimited faith in the possible, belief in the existence of independent beings bearing within themselves the principle of their strength,—an idea quite opposed to Christianity, which in such beings necessarily sees either angels or fiends. And besides, these strange beings are always presented as being outside the pale of the Church; and when the knight of the Round Table has conquered them, he forces them to go and pay homage to Guinevere, and have themselves baptised.
Now, if in poetry there is a marvellous element that we might accept, surely it is this. Classical mythology, taken in its first simplicity, is too bold, taken as a mere figure of rhetoric, too insipid, to give us satisfaction. As to the marvellous element in Christianity, Boileau is right: no fiction is compatible with such a dogmatism. There remains then the purely naturalistic marvellous, nature interesting herself in action and acting herself, the great mystery of fatality unveiling itself by the secret conspiring of all beings, as in Shakespeare and Ariosto. It would be curious to ascertain how much of the Celt there is in the former of these poets; as for Ariosto he is the Breton poet par excellence. All his machinery, all his means of interest, all his fine shades of sentiment, all his types of women, all his adventures, are borrowed from the Breton romances.