In these tales we have two main elements, one real and one ideal. The real element is the fact that the ancient Irish unquestionably made voyages and visited lands which the fervid Celtic imagination and the lapse of time transformed into the wonderful regions of the legends. The stories are thus early geographies, and they show unmistakably a knowledge of western Europe and of the Canary Islands or some other tropical regions; perhaps also, some have gone so far as to claim, they are reminiscent of voyages to America.

The ideal element is no less important as indicating achievement, for it shows that the Irish poets of pagan times had not only realized, but had succeeded in making their national traditions embody, the fact that love of justice and aspiration for knowledge are the foundations of all enduring human achievement and all perfect human joy. Christianity therefore found moral and spiritual ideas of a highly developed order in pagan Ireland, and it did not hesitate to adopt whatever in the literature of the country illustrated its own teachings, and not only were these stories of visits to the other world full of suggestions as to ways of enforcing Christian doctrine, but the Irish church and men of Irish birth were the most active in spreading the faith in the early centuries of its conquest of western Europe.

For these reasons it is not strange that all the earliest Christian visions of the spirit-world were of Irish origin. We find the earliest in the Ecclesiastical History of the "Venerable Bede," who died in 735. It is the story of how an Irishman of great sanctity, Furseus by name, was taken in spirit by three angels to a place from which he looked down and saw the four fires that are to consume the world: those of falsehood, avarice, discord, fraud and impiety. In this there is the germ of some very fundamental things in Dante's poem, and we know that Dante knew Bede and had probably read his history, for he places him in Paradise and mentions him elsewhere in his works.

In Bede's work there is also another vision, and though in this second case the man who visits the spirit-world is not an Irishman, but a Saxon named Drithelm, yet the story came to Bede through an Irish monk named Haemgils; so it, too, is connected with Ireland, and it also contains much that is developed further in the Divine Comedy.

One of the most celebrated of the works belonging to this class of so-called "visionary" writings is the Fis or "Vision" which goes under the name of the famous Irish saint, Adamnan, who was poetically entitled the "High Scholar of the Western World." This particular vision, the Fis Adamnáin, is remarkable among other things for its literary quality, which is far superior to anything of the time, and for the fact that it represents "the highest level of the school to which it belonged," and that it is "the most important contribution made to the growth of the legend within the Christian Church prior to the advent of Dante."

Another Irish vision of great popularity all over Europe in the Middle Ages is the Voyage of Saint Brendan. This is known as the Irish Odyssey, and it is similar to the pagan tales of Maelduin and Bran, except that instead of its hero being a dauntless warrior seeking vengeance or a noble youth seeking happiness, he is a Christian saint in quest of peace; and instead of the perils of the way being overcome by physical force or the favor of some capricious pagan deity, they are averted by the power of faith and virtue.

The Voyage of Saint Brendan, like its pagan predecessors, has a real and an ideal basis; and in both respects it shows an advancement over its prototypes. It contains some very poetic touches, and is credited with being the source of some of the most effective features of Dante's poem. Its great popularity is shown by the fact that Caxton, the first English printer, published a translation of it in 1483; so that it was among the first books printed in English, and for that reason must have been one of the best-known works of the time. Dante undoubtedly knew it, for he was a great scholar in the learning of his day, and especially in ecclesiastical history and the biography of saints.

Another vision of Irish origin that Dante and other writers have borrowed from is that of an Irish soldier named Tundale. He is said to have been a very wicked and proud man, who refused to a friend who owed him for three horses an extension of time in which to pay for them. For this he was struck down by an invisible hand so that he remained apparently dead from Wednesday till Saturday, when he revived and told a story of a visit to the world of the dead that has many features later embodied in the Divine Comedy. Tundale's vision is said to have taken place in 1149; Dante probably wrote his poem between 1314 and 1321.

The Irish also produced another legend of this sort that was enormously and universally popular, and became the chief authority on the nature of heaven and hell, in the story of Saint Patrick's Purgatory. Saint Patrick was said to have been granted a view of heaven and hell, and a certain island in Lough Derg in Donegal was reputed to be the spot in which he had begun his journey; and there, it was said, those who desired to purge themselves of their sins could enter as he had entered and come back to the world again, provided their faith was strong enough.

This legend was probably known in Ireland from a very early time, but it had spread over all western Europe by the twelfth century. Henry of Saltrey, a Benedictine monk of the Abbey of that name in England, wrote an account in Latin of the descent of an Irish soldier named Owen into Saint Patrick's Purgatory in 1153; and this story soon became the subject of poetic treatment all over Europe. We have several French versions, one by the celebrated French poetess Marie de France, who lived about 1200; and there are others in all the languages of Europe, besides evidence of its wide circulation in the original Latin. Its importance is shown by the fact that it is mentioned by Matthew Paris, the chief English historian of the thirteenth century, and also by Froissart, the well-known French annalist of the fourteenth while Calderon, the great Spanish dramatist, has written a play based on the legend. Dante undoubtedly knew of Marie de France's version as well as the original of Henry of Saltrey and probably others besides.