Both the soul and the Supersoul, they are situated within the heart. Īśvaraḥ sarva-bhūtānāṁ hṛd-deśe (BG 18.61). It is not said that "Anywhere in the body it is sitting." No. Hṛd-deśe, in the heart. And actually, by medical science, the heart is the center of all activities of the body, office. And the brain is the manager. The director is there, Kṛṣṇa. He says also in another place, sarvasya cāhaṁ hṛdi sanniviṣṭaḥ. Everything is clear. Sarvasya cāhaṁ hṛdi sanniviṣṭaḥ, "I am sitting in everyone's heart." Find out God, find out Kṛṣṇa. In several places, all Vedic literature, guhāyām. Guhāyām means in the heart. Sarvasya cāhaṁ hṛdi sanniviṣṭo mattaḥ smṛtir jñānam apohanaṁ ca (BG 15.15). The supreme director, Kṛṣṇa, is sitting there, and He is directing, "Now this living entity wants to fulfill his desire in this way." He's giving direction to the material nature. "Now, prepare a vehicle, body, for this rascal in this way. He wants to enjoy. All right, let him enjoy." This is going on. We are all rascals, we are manufacturing our different ways of life. "I think." So you are thinking. As soon as you are thinking... But we cannot fulfill our desires without sanction of God. That is not possible. But because we are persisting, that "I want to fulfill my desire in this way," Kṛṣṇa is sanctioning, "All right." Just like a child persists to possess something. The father gives, "All right, take it." So all these bodies we are getting, although by the sanction of the Supreme Lord, but He is sanctioning with reluctance that "Why this rascal is wanting like this?" This is our position. Therefore, at last Kṛṣṇa says, sarva-dharmān parityajya, (BG 18.66) "Give up this rascaldom, 'I want this body, I want that body, I want to enjoy life in this way'—give up all this nonsense."
So here in the Vedic literatures we find that both the Lord and the living entity, they are situated in the heart. The living entity, jīva, is desiring, and the master is sanctioning, and the prakṛti or the material nature is giving the body. "Here is the body, ready, sir. Come here." Therefore the original cause of our entanglement or liberation is our desire.