"Intellectual superiority is not always accompanied by an equal degree of moral superiority, and the greatest geniuses may have much to expiate. For this reason, they often have to undergo an existence inferior to the one they have previously accomplished, which is a cause of suffering for them the hindrances to the manifestation of his faculties thus imposed upon a spirit being like chains that fetter the movements of a vigorous man. The idiot may be said to be lame in the brain, as the halt is lame in the legs, and the blind, in the eyes."

“The Gospel According to Spiritism by Allan Kardec”

“If there be a doctrine that should win over the most incredulous by its charm and its beauty, it is that of the existence of spirit-protectors, or guardian-angels. To think that you have always near you beings who are superior to you, and who are always beside you to counsel you, to sustain you, to aid you in climbing the steep ascent of self-improvement, whose friendship is truer and more devoted than the most intimate union that you can contract upon the earth-is not such an idea most consoling? Those beings are near you by the command of God. It is He who has placed them beside you. They are there for love of Him, and they fulfil towards you a noble but laborious mission. They are with you wherever you may be; in the dungeon, in solitude, in the lazar-house, even in the haunts of debauchery. Nothing ever separates you from the friend whom you cannot see, but whose gentle impulsions are felt, and whose wise monitions are heard, in the innermost recesses of your heart.”

“The spirit acquires an increase of knowledge and experience in each of his corporeal existences. He loses sight of part of these gains during his reincarnation in matter, which is too gross to allow of his remembering them in their entirety; but he remembers them as a spirit. It is thus that some somnambulists give evidence of possessing knowledge beyond their present degree of instruction, and even of their apparent intellectual capacity. The intellectual and scientific inferiority of a somnambulist in his waking state, therefore, proves nothing against his possession of the knowledge he may display in his lucid state. According to the circumstances of the moment and the aim proposed, he may draw this knowledge from the stores of his own experience, from his clairvoyant perception of things actually occurring, or from the counsels which he receives from other spirits; but, in proportion as his own spirit is more or less advanced, he will make his statements more or less correctly.”

“As spirits transport themselves from point to point with the rapidity of thought, they may be said to see everywhere at the same time. A spirit's thought may radiate at the same moment on many different points; but this faculty depends on his purity. The more impure the spirit, the narrower is his range of sight. It is only the higher spirits who can take in a whole at a single glance.”

“Spirits incarnate themselves as men or as women, because they are of no sex and, as it is necessary for them to develop themselves in every direction, both sexes, as well as every variety of social position. furnish them with special trials and duties, and with the opportunity of acquiring experience. A spirit who had always incarnated itself as a man would be only known by men, and vice versa.”

“The Spirits' Book codified by Allan Kardec or as HTML”