The source of the realization of God is, in the words of the Quran, reflection (tafakkur and tadabbur). (The Quran, 3:191) The attainment of God-realization by contemplation is entirely a function of the mind. In the human body, the act of thinking is done only by the brain. What is achieved by this process of thinking has been defined as God-realization.

In ancient times, there were groups of spiritual persons who held that the source of realization of God was the heart, and it was due to this concept that the method of meditation, by focusing on the heart became prevalent. But this concept does not relate to divine religion. This concept derived from the concept of monism. Those who believe in monism cherish the belief that God is in-dwelling. He is lodged in one’s heart. But all these theories are based on supposition. There are no real arguments in support of them.

With reference to the heart, the Quran uses the word “understanding” (fiqh) (7:179), but this word “heart” is used only as a metaphor. It is not used in the actual physical sense. Those who have done research in the functioning of the heart have come to the conclusion that during the circulation of the blood there is communication between heart and mind. But this does not prove the theory of a thinking heart, because such communication takes place between all of the organs and the mind. According to modern medical studies what has been proved is that communication does take place between organs but that neither the heart nor any other organ besides the mind possesses the ability to think.

The truth is that all the organs of the body are subservient to the brain, and in this, the heart is no exception.

Source: Discovering God