The Lord tells Arjuna that basically there is no possibility of understanding the Supreme Truth, the Absolute Truth, the Supreme Personality of Godhead, simply by speculating, for the Supreme Truth is so great that it is not possible to understand Him or to achieve Him simply by making a mental effort. Man can go on speculating for several millions of years, and if he is not devoted, if he is not a lover of the Supreme Truth, he will never understand Krishna, or the Supreme Truth. Only by devotional service is the Supreme Truth, Krishna, pleased, and by His inconceivable energy He can reveal Himself to the heart of the pure devotee. The pure devotee always has Krishna within his heart; and with the presence of Krishna, who is just like the sun, the darkness of ignorance is at once dissipated. This is the special mercy rendered to the pure devotee by Krishna
The distinction between the jiva and the isvara will be explained in the Thirteenth Chapter of Bhagavad-gita. The Lord is kshetra-jna, conscious, as is the living being, but the living being is conscious of his particular body, whereas the Lord is conscious of all bodies. Because He lives in the heart of every living being, He is conscious of the psychic movements of the particular jivas. We should not forget this. It is also explained that the Paramatma, the Supreme Personality of Godhead, is living in everyone’s heart as isvara, as the controller, and that He is giving directions for the living entity to act as he desires. The living entity forgets what to do. First of all he makes a determination to act in a certain way, and then he is entangled in the actions and reactions of his own karma. After giving up one type of body, he enters another type of body, as we put on and take off clothes.
if we accept the Vedic conclusion as stated in the Bhagavad-gita that these material bodies are perishable in due course of time (antavanta ime dehah) but that the soul is eternal (nityasyoktah saririnah), then we must remember always that the body is like a dress; therefore why lament the changing of a dress? The material body has no factual existence in relation to the eternal soul. It is something like a dream. In a dream we may think of flying in the sky, or sitting on a chariot as a king, but when we wake up we can see that we are neither in the sky nor seated on the chariot. The Vedic wisdom encourages self-realization on the basis of the nonexistence of the material body. Therefore, in either case, whether one believes in the existence of the soul or one does not believe in the existence of the soul, there is no cause for lamentation for loss of the body.
One may question here that if Krishna is equal to everyone and no one is His special friend, then why does He take a special interest in the devotees who are always engaged in His transcendental service? But this is not discrimination; it is natural. Any man in this material world may be very charitably disposed, yet he has a special interest in his own children. The Lord claims that every living entity — in whatever form — is His son, and so He provides everyone with a generous supply of the necessities of life. He is just like a cloud which pours rain all over, regardless of whether it falls on rock or land or water. But for His devotees, He gives specific attention. Such devotees are mentioned here: they are always in Krishna consciousness, and therefore they are always transcendentally situated in Krishna.
In this verse the word buddhi-yogam is very significant. We may remember that in the Second Chapter the Lord, instructing Arjuna, said that He had spoken to him of many things and that He would instruct him in the way of buddhi-yoga. Now buddhi-yoga is explained. Buddhi-yoga itself is action in Krishna consciousness; that is the highest intelligence. Buddhi means intelligence, and yoga means mystic activities or mystic elevation. When one tries to go back home, back to Godhead, and takes fully to Krishna consciousness in devotional service, his action is called buddhi yoga. In other words, buddhi-yoga is the process by which one gets out of the entanglement of this material world. The ultimate goal of progress is Krishna. People do not know this; therefore the association of devotees and a bona fide spiritual master are important. One should know that the goal is Krishna, and when the goal is assigned, then the path is slowly but progressively traversed, and the ultimate goal is achieved.