The smallness of fairies, which has just been considered, and the belief in changelings are the two most prominent characteristics of the Fairy-Faith, according to our evidence in chapter ii; and we are now to consider the second. The prevalent and apparently the only important theories which are current to explain this belief in changelings may be designated as the Kidnap Theory and the Human-Sacrifice Theory. These we shall proceed to estimate, after which there will be introduced newer and seemingly more adequate theories. _Kidnap Theory_ Some writers have argued that the changeling belief merely reflects a time when the aboriginal pre-Celtic peoples held in subjection by the Celts, and forced to live in mountain caverns and in secret retreats underground, occasionally kidnapped the children of their conquerors, and that such kidnapped children sometimes escaped and told to their Celtic kinsmen highly romantic tales about having been in an underground fairy-world with fairies. Frequently this argument has taken a slightly different form: that instead of unfriendly pre-Celtic peoples it was magic-working Druids who--either through their own choice or else, having been driven to bay by the spread of Christianity, through force of circumstances--dwelt in secret in chambered mounds or souterrains, or in dense forests, and then stole young people for recruits, sometimes permitting them, years afterwards, when too old to be of further use, to return home under an inviolable vow of secrecy.[150] And Mr. David MacRitchie in supporting his own Pygmy Theory has made interesting modern elaborations of these two slightly different theories concerning changelings.[151] As already pointed out, there are definite ethnological elements blended in the other parts of the complex Fairy-Faith; and so in this part of it, the changeling belief, there are conceivably more of such elements which lend some support to the Kidnap Theory. In itself, however, as we hope to show conclusively, the Theory, failing to grasp the essential and underlying character of this belief, does not adequately explain it. _Human-Sacrifice Theory_