On that theory the god of the thunder and the sky was derived from the original god of the oak; on the present theory, which I now prefer, the god of the sky and the thunder was the great original deity of our Aryan ancestors, and his association with the oak was merely an inference based on the frequency with which the oak was seen to be struck by lightning. If the Aryans, as some think, roamed the wide steppes of Russia or Central Asia with their flocks and herds before they plunged into the gloom of the European forests, they may have worshipped the god of the blue or cloudy firmament and the flashing thunderbolt long before they thought of associating him with the blasted oaks in their new home.
Perhaps the new theory has the further advantage of throwing light on the special sanctity ascribed to mistletoe which grows on an oak. The mere rarity of such a growth on an oak hardly suffices to explain the extent and the persistence of the superstition. A hint of its real origin is possibly furnished by the statement of Pliny that the Druids worshipped the plant because they believed it to have fallen from heaven and to be a token that the tree on which it grew was chosen by the god himself. Can they have thought that the mistletoe dropped on the oak in a flash of lightning? The conjecture is confirmed by the name thunder-besom which is applied to mistletoe in the Swiss canton of Aargau, for the epithet clearly implies a close connexion between the parasite and the thunder; indeed thunder-besom is a popular name in Germany for any bushy nest-like excrescence growing on a branch, because such a parasitic growth is actually believed by the ignorant to be a product of lightning. If there is any truth in this conjecture, the real reason why the Druids worshipped a mistletoe-bearing oak above all other trees of the forest was a belief that every such oak had not only been struck by lightning but bore among its branches a visible emanation of the celestial fire; so that in cutting the mistletoe with mystic rites they were securing for themselves all the magical properties of a thunder-bolt. If that was so, we must apparently conclude that the mistletoe was deemed an emanation of the lightning rather than, as I have thus far argued, of the midsummer sun.
Perhaps, indeed, we might combine the two seemingly divergent views by supposing that in the old Aryan creed the mistletoe descended from the sun on Midsummer Day in a flash of lightning. But such a combination is artificial and unsupported, so far as I know, by any positive evidence. Whether on mythical principles the two interpretations can really be reconciled with each other or not, I will not presume to say; but even should they prove to be discrepant, the inconsistency need not have prevented our rude forefathers from embracing both of them at the same time with an equal fervour of conviction; for like the great majority of mankind the savage is above being hidebound by the trammels of a pedantic logic. In attempting to track his devious thought through the jungle of crass ignorance and blind fear, we must always remember that we are treading enchanted ground, and must beware of taking for solid realities the cloudy shapes that cross our path or hover and gibber at us through the gloom. We can never completely replace ourselves at the standpoint of primitive man, see things with his eyes, and feel our hearts beat with the emotions that stirred his. All our theories concerning him and his ways must therefore fall far short of certainty; the utmost we can aspire to in such matters is a reasonable degree of probability.
To conclude these enquiries we may say that if Balder was indeed, as I have conjectured, a personification of a mistletoe-bearing oak, his death by a blow of the mistletoe might on the new theory be explained as a death by a stroke of lightning. So long as the mistletoe, in which the flame of the lightning smouldered, was suffered to remain among the boughs, so long no harm could befall the good and kindly god of the oak, who kept his life stowed away for safety between earth and heaven in the mysterious parasite; but when once that seat of his life, or of his death, was torn from the branch and hurled at the trunk, the tree fellthe god diedsmitten by a thunderbolt.
And what we have said of Balder in the oak forests of Scandinavia may perhaps, with all due diffidence in a question so obscure and uncertain, be applied to the priest of Diana, the King of the Wood, at Aricia in the oak forests of Italy. He may have personated in flesh and blood the great Italian god of the sky, Jupiter, who had kindly come down from heaven in the lightning flash to dwell among men in the mistletoethe thunder-besomthe Golden Boughgrowing on the sacred oak in the dells of Nemi. If that was so, we need not wonder that the priest guarded with drawn sword the mystic bough which contained the god's life and his own. The goddess whom he served and married was herself, if I am right, no other than the Queen of Heaven, the true wife of the sky-god. For she, too, loved the solitude of the woods and the lonely hills, and sailing overhead on clear nights in the likeness of the silver moon looked down with pleasure on her own fair image reflected on the calm, the burnished surface of the lake, Diana's Mirror.