"Who is it that interrogates? Who is it that answers? There is no doubt that it is the spirit ..."

... "When you wish to reflect upon or consider a matter, you consult something within you. You say, shall I do it, or shall I not do it? Is it better to make this journey or abandon it? Whom do you consult? Who is within you deciding this question? Surely there is a distinct power, an intelligent ego. Were it not distinct from your ego, you would not be consulting it. It is greater than the faculty of thought. It is your spirit which teaches you, which advises and decides upon matters. Who is it that interrogates? Who is it that answers? There is no doubt that it is the spirit and that there is no change or transformation in it, for it is not a composition of elements, and anything that is not composed of elements is eternal. Change and transformation are peculiarities of composition. There is no change and transformation in the spirit. In proof of this, the body may become weakened in its members. It may be dismembered, or one of its members may be incapacitated. The whole body may be paralyzed; and yet the mind, the spirit, remains ever the same. The mind decides; the thought is perfect; and yet the hand is withered, the feet have become useless, the spinal column is paralyzed, and there is no muscular movement at all, but the spirit is in the same status. Dismember a healthy man; the spirit is not dismembered. Amputate his feet; his spirit is there. He may become lame; the spirit is not affected. The spirit is ever the same; no change or transformation can you perceive, and because there is no change or transformation, it is everlasting and permanent.

Consider man while in the state of sleep; it is evident that all his parts and members are at a standstill, are functionless. His eye does not see, his ear does not hear, his feet and hands are motionless; but, nevertheless, he does see in the world of dreams, he does hear, he speaks, he walks, he may even fly in an airplane. Therefore, it becomes evident that though the body be dead, yet the spirit is alive and permanent. Nay, the perceptions may be keener when man’s body is asleep, the flight may be higher, the hearing may be more acute; all the functions are there, and yet the body is at a standstill. Hence, it is proof that there is a spirit in the man, and in this spirit there is no distinction as to whether the body be asleep or absolutely dead and dependent. The spirit is not incapacitated by these conditions; it is not bereft of its existence; it is not bereft of its perfections. The proofs are many, innumerable.

These are all rational proofs. Nobody can refute them. As we have shown that there is a spirit and that this spirit is permanent and everlasting, we must strive to learn of it. May you become informed of its power, hasten to render it divine, to have it become sanctified and holy and make it the very light of the world illumining the East and the West."

`Abdu'l-Bahá, The Promulgation of Universal Peace, pp. 242-243

24 July 1912 
(excerpt from) Talk to Theosophical Society 
The Kensington Exeter and Boylston Streets, 
Boston, Massachusetts