and the Sunnah of His Messenger ﷺ, to trample it underfoot and give it no consideration.

Thus the heart is un­questionably the seat of intellect, while the brain is the place of perception and mental imaging. The brain first conceives an idea and prepares it, then dispatches it to the heart; the heart, in turn, issues the command or the prohibition. It is as though the brain is only a secretary that drafts matters and passes them on to the heart, after which the heart directs, orders, or forbids. This is not at all strange: “And in your own selves—will you not then see?” (Adh-Dhāriyāt 51:21). Inside the human body are marvels that leave minds bewildered, so it is no wonder that Allah, exalted be He, has placed perception in the head: the brain formulates and arranges matters, and when nothing remains but to issue commands, it sends them to the heart; then the heart sets things in motion—commanding or forbidding.

The Prophet ﷺ said, “When it is sound, the whole body is sound.” If authority did not reside in the heart, it would not be that when it is sound the entire body is sound and when it is corrupt the entire body is corrupt.

Therefore, the hearts are the locus of reason and the organ that manages a person. Yet they are undeniably connected to the brain; hence, when the brain is impaired, thought and reason become impaired as well—the two are linked. Still, the directing intellect is in the heart, and the heart is in the chest: “but it is the hearts within the breasts that become blind” (Al-Hajj 22:46).