According to the scientists of consciousness, there are several distinct stages of the Yogic trance, or Samadhi, depending on how deeply or intensely one is absorbed in the inner awareness, and whether or not there remains any “seed” which relates the being back into the manifested world. The earlier stages of this trance, to be sure, block out the running of the mind after the impressions of the senses, but they are not as deep and not as impervious to response as the later and deeper stages of the experience.
Sri Aurobindo describes the general stages of the Yogic trance: “Samadhi or Yogic trance retires to increasing depths according as it draws farther and farther away from the normal or waking state and enters into degrees of consciousness less and less communicable to the waking mind, less and less ready to receive a summons from the waking world. Beyond a certain point the trance becomes complete and it is then almost or quite impossible to awaken or call back the soul that has receded into them; it can only come back by its own will or at most by a violent shock of physical appeal dangerous to the system owing to the abrupt upheaval of the return. There are said to be supreme states of trance in which the soul persisting for too long a time cannot return; for it loses its hold on the cord which binds it to the consciousness of life, and the body is left, maintained indeed in its set position, not dead by dissolution, but incapable of recovering the ensouled life which had inhabited it. Finally, the Yogin acquires at a certain stage of development the power of abandoning his body definitively without the ordinary phenomena of death, by an act of will, or by a process of withdrawing the pranic life-force through the gate of the upward life-current …, opening for it a way through the mystic brahmarandhra in the head. By departure from life in the state of Samadhi he attains directly to that higher status of being to which he aspires.”
Inasmuch as the experience in the Yogic trance is related to the superconscient levels of awareness, it becomes virtually impossible for the seeker to bring back and communicate the experience to the waking mind. This is also the rationale behind the need to enter the trance to experience these superconscient states. Until such time as the evolutionary process opens up pathways of energy and communication between the mental consciousness and the higher levels, the seeker finds that he must abandon, at least temporarily, the one in order to experience the other. The impression of this experience, and the repetition of it, begin to shape and prepare the mental awareness for the new and more subtle, yet more powerful forces that are awake in the superconscient planes of awareness.
Swami Vivekananda, in his famous series of lectures on Raja Yoga makes the following commentary about the difference between ordinary sleep and the state of Samadhi. “No enlightenment comes. But when a man goes into Samadhi, if he goes into it a fool, he comes out a sage. What makes the difference? From one state a man comes out the very same man that he went in, and from another state the man comes out enlightened, a sage, a prophet, a saint, his whole character changed, his life changed, illumined. (Swami Vivekananda, Raja Yoga, Chapter 7, Dhyana and Samadhi).
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 26, Samadhi, pp. 499-500