In the scriptures the word 'guru' has been used in two senses. One is the guru who dispels the darkness, and the other is the guru from whom we receive the mantra of initiation. Guru is he who guides us in our spiritual sadhana. There is an important chakra in the body known as ajna chakra, or the guru chakra. It is located behind the eyebrow centre, at the top of the spine, where ida, pingala and sushumna merge into one channel.
Ajna chakra has a unique quality: in the process of sadhana, as the external awareness of the sadhaka becomes inactive, this chakra becomes progressively and proportionately active. On the one side, the functions of the senses, manas, buddhi and chitta are withdrawn, and on the other side, the form of the ishta devata, or personal deity, becomes clearer and ajna chakra awakens simultaneously. As soon as the senses become extroverted, ajna chakra becomes dormant. The awakening of ajna chakra takes place during meditation only in those sadhakas whose senses are withdrawn and whose mind has become calm and detached to a considerable extent.
There are some sadhakas whose ajna chakra remains awake during meditation and even when not in meditation. However, such people are rare. In the state of deep meditation, when all the senses are withdrawn, ajna chakra receives the subtle instructions of the guru. Other than this, all the peepholes of perception are closed in this state. There is a membrane in between the gross and subtle states that acts as a soundproofing device. When you are in the gross state, you do not hear the subtle sounds, and when you cross over into the subtle state, you cannot hear the gross sounds. The experiences of one area do not have entry into the other area. The senses are capable of perceiving only specific vibrations within a particular range, even though sound waves of all frequencies exist constantly.
In deep meditation the instructions are not generated by thought, as thought is a product of the mind, which is gross. The guru instructs the disciple through a subtle form of communication known as transmission. Only those gurus who are able to remain in the subtle state can convey subtle instructions. However, it is very difficult to remain for long periods in the subtle state, where no karma or activity can take place. Two swords cannot be placed in one sheath. All actions have to be abandoned, whether direct or indirect, in order to remain in this state. It is necessary to give up all worldly attachments, erase all impressions of pleasure and pain, rise above the pull of the senses, mind and intellect, and have no distinctions between the auspicious and inauspicious. This caliber of guru is seldom available.
When such a guru transmits instructions to his disciple during meditation, a counter vibration occurs in the disciple's ajna chakra that takes him further on the path of sadhana. The moment the arrow of the guru's instruction hits the disciple, he feels as if he has crossed over from a small dark room into a vast space. This space does not appear as a special world of memories and dreams; it is exactly like the gross world in appearance, with all the same perceptions. This internal world is identical to the external world with only one difference: the external world is perishable, whereas the internal world is eternal. After reaching the internal world, the external world appears to be false.
This experience is only possible when ajna chakra is unlocked and the commands of the guru are heard there. After this stage, the sadhaka does not do any other sadhana except obeying the words of the guru. Until this point, he undertakes different sadhanas to awaken ajna chakra, but beyond this point, only the transmission of the guru can take him further. On proceeding further, he perceives the light of the Atma and has the experience that he and the Atma are one and the same. There is no difference between the two. This is the phenomenon of Jaanat tumahi tumahi hoi jaaee– "On knowing you, I become you." This is the goal of all yogas and sadhanas.