Here, again, this new prehistoric philosophy gave an added interest to life, but it was none the less a source of fresh terrors.

The world swarmed with invisible spirits, some friendly, some hostile, and, in view of these beings, life had to be regulated by strict rules of actions and prohibitions.

Even in the neolithic stage the inhabitants of Celtic countries had attained to the religious ideas in question, as is seen not only by their folk-lore and by the names of groups of goddesses such as the Matres (or mothers), but by the fact that in historic times they had advanced well beyond this stage to that of named and individualised gods.

As in all countries where the gods were individualised, the men of Celtic lands, whether aborigines or invaders, had toiled along the steep ascent from the primitive vague sense of being haunted to a belief in gods who, like Esus, Teutates, Grannos, Bormanus, Litavis, had names of a definite character.
Among the prohibitions which had established themselves among the races of Celtic lands, as elsewhere, was that directed against the shedding of the blood of one's own kin.

There are indications, too, that some at any rate of the tribes inhabiting these countries reckoned kinship through the mother, as in fact continued to be the case among the Picts of Scotland into historic times.