Most of these stories no longer exist in their primitive form, and various ideas are found in them—conception by magical means, divine descent through the amour of a divinity and a mortal, and rebirth.
As to the first, the help of magician or priest is often invoked in savage society and even in European folk-custom in case of barrenness. Prayers, charms, potions, or food are the means used to induce conception, but perhaps at one time these were thought to cause it of themselves. In many tales the swallowing of a seed, fruit, insect, etc., results in the birth of a hero or heroine, and it is probable that these stories embody actual belief in such a possibility. If the stories of Conall Cernach and Aed Slane are not attenuated instances of rebirth, say, of the divinity of a well, they are examples of this belief. The gift of fruitfulness is bestowed by Druid and saint, but in the story of Conall it is rather the swallowing of the worm than the Druid's incantation that causes conception, and is the real motif of the tale.
Where the rebirth of a divinity occurs as the result of the swallowing of a small animal, it is evident that the god has first taken this form. The Celt, believing in conception by swallowing some object, and in shape-shifting, combined his information, and so produced a third idea, that a god could take the form of a small animal, which, when swallowed, became his rebirth.[1205] If, as the visits of barren women to dolmens and megalithic monuments suggest, the Celts believed in the possibility of the spirit of a dead man entering a woman and being born of her or at least aiding conception,—a belief held by other races,[1206]—this may have given rise to myths regarding the rebirth of gods by human mothers. At all events this latter Celtic belief is paralleled by the American Indian myths, e.g. of the Thlinkeet god Yehl who transformed himself now into a pebble, now into a blade of grass, and, being thus swallowed by women, was reborn.
In the stories of Etain and of Lud, reborn as Setanta, this idea of divine transformation and rebirth occurs. A similar idea may underlie the tale of Fionn and Mongan. As to the tales of Gwion and the Swineherds, the latter the servants of gods, and perhaps themselves regarded once as divinities, who in their rebirth as bulls are certainly divine animals, they present some features which require further consideration. The previous transformations in both cases belong to the Transformation Combat formula of many Märchen, and obviously were not part of the original form of the myths. In all such Märchen the antagonists are males, hence the rebirth incident could not form part of them. In the Welsh tale of Gwion and in the corresponding Taliesin poem, the ingenious fusion of the Märchen formula with an existing myth of rebirth must have taken place at an early date.[1207] This is also true of The Two Swineherds, but in this case, since the myth told how two gods took the form of worms and were reborn of cows, the formula had to be altered. Both remain alive at the end of the combat, contrary to the usual formula, because both were males and both were reborn. The fusion is skilful, because the reborn personages preserve a remembrance of their former transformations,[1208] just as Mongan knows of his former existence as Fionn. In other cases there is no such remembrance. Etain had forgotten her former existence, and Cúchulainn does not appear to know that he is a rebirth of Lug.
The relation of Lug to Cúchulainn deserves further inquiry. While the god is reborn he is also existing as Lug, just as having been swallowed as a worm by Dechtire, he appears in his divine form and tells her he will be born of her. In the Táin he appears fighting for Cúchulainn, whom he there calls his son. There are thus two aspects of the hero's relationship to Lug; in one he is a rebirth of the god, in the other he is his son, as indeed he seems to represent himself in The Wooing of Emer, and as he is called by Laborcham just before his death.[1209] In one of the birth-stories he is clearly Lug's son by Dechtire. But both versions may simply be different aspects of one belief, namely, that a god could be reborn as a mortal and yet continue his divine existence, because all birth is a kind of rebirth. The men of Ulster sought a wife for Cúchulainn, "knowing that his rebirth would be of himself," i.e. his son would be himself even while he continued to exist as his father. Examples of such a belief occur elsewhere, e.g. in the Laws of Manu, where the husband is said to be reborn of his wife, and in ancient Egypt, where the gods were called "self-begotten," because each was father to the son who was his true image or himself. Likeness implied identity, in primitive belief. Thus the belief in mortal descent from the gods among the Celts may have involved the theory of a divine avatar. The god became father of a mortal by a woman, and part of himself passed over to the child, who was thus the god himself.
Conchobar was also a rebirth of a god, but he was named from the river whence his mother had drawn water containing the worms which she swallowed. This may point to a lost version in which he was the son of a river-god by Nessa. This was quite in accordance with Celtic belief, as is shown by such names as Dubrogenos, from dubron, "water," and genos, "born of"; Divogenos, Divogena, "son or daughter of a god," possibly a river-god, since deivos is a frequent river name; and Rhenogenus, "son of the Rhine."[1210] The persons who first bore these names were believed to have been begotten by divinities. Mongan's descent from Manannan, god of the sea, is made perfectly clear, and the Welsh name Morgen = Morigenos, "son of the sea," probably points to a similar tale now lost. Other Celtic names are frequently pregnant with meaning, and tell of a once-existing rich mythology of divine amours with mortals. They show descent from deities—Camulogenus (son of Camulos), Esugenos (son of Esus), Boduogenus (son of Bodva); or from tree-spirits—Dergen (son of the oak), Vernogenus (son of the alder); or from divine animals—Arthgen (son of the bear), Urogenus (son of the urus).[1211] What was once an epithet describing divine filiation became later a personal name. So in Greece names like Apollogenes, Diogenes, and Hermogenes, had once been epithets of heroes born of Apollo, Zeus, and Hermes.
Thus it was a vital Celtic belief that divinities might unite with mortals and beget children. Heroes enticed away to Elysium enjoyed the love of its goddesses—Cúchulainn that of Fand; Connla, Bran, and Oisin that of unnamed divinities. So, too, the goddess Morrigan offered herself to Cúchulainn. The Christian Celts of the fifth century retained this belief, though in a somewhat altered form. S. Augustine and others describe the shaggy demons called dusii by the Gauls, who sought the couches of women in order to gratify their desires.[1212] The dusii are akin to the incubi and fauni, and do not appear to represent the higher gods reduced to the form of demons by Christianity, but rather a species of lesser divinities, once the object of popular devotion.
These beliefs are also connected with the Celtic notions of transformation and transmigration—the one signifying the assuming of another shape for a time, the other the passing over of the soul or the personality into another body, perhaps one actually existing, but more usually by actual rebirth. As has been seen, this power of transformation was claimed by the Druids and by other persons, or attributed to them, and they were not likely to minimise their powers, and would probably boast of them on all occasions. Such boasts are put into the mouths of the Irish Amairgen and the Welsh Taliesin. As the Milesians were approaching Ireland, Amairgen sang verses which were perhaps part of a ritual chant:
"I am the wind which blows over the sea,
I am the wave of the ocean,