275. Among the causes that might oppose the manifestation of a spirit, some are personal to him, some foreign. We must place among the former his occupations, or the missions in which he is engaged, and from which he cannot turn aside to yield to our wishes; in such case, his visit is only postponed.
There is, again, his own situation. While the state of incarnation may not be an absolute obstacle, it may be a hindrance at certain given, moments, especially when it takes place in inferior worlds, and when the spirit himself is. but little dematerialized. In the superior worlds, in those where the ties of spirit and matter are very feeble, the manifestation is almost as easy as in the wandering state, and in all cases easier than in those where the corporeal matter is more compact.
The foreign causes pertain principally to the nature of the medium, to that of the invoker, to the sphere in which the invocation is made, and, lastly, to the end proposed. Some mediums receive more especially communications from their familiar spirits, who may be more or less elevated ; others are capable of serving as intermediaries to all spirits ; that depends on the sympathy or antipathy, the attraction or repulsion, which the personal spirit of the medium exercises over the foreign spirit, who may take him for interpreter with pleasure or with repugnance. That, again, setting aside the innate qualities of the medium, depends on the development of the medianimic faculty. Spirits come more willingly, are more explicit with a medium who offers them no material obstacle. All things, besides, being equal as to moral conditions, the greater facility a medium has in writing or expressing himself the more his relations with the spirit world may be generalized.