The heart that pumps blood and the heart that perceives truth are, in this tradition, the same organ described twice.
A modern reader encountering “the heart” in a religious text usually reads it as a metaphor for feeling — the seat of emotion, set against the head’s cold reason. The qalb in Islamic thought does something stranger: it is presented as an organ of cognition in its own right, capable of a kind of seeing that the physical eyes cannot do alone.
Al-Ghazali distinguished the physical heart — the blood-pumping organ, part of the visible world — from a second sense: a “subtle spiritual substance” constituting a person’s true essence, the actual seat of reasoning, intention, and decision. In the Qur’an itself, the qalb functions as a real center of perception, understanding, and moral orientation — which is why a “hardened” or “sealed” heart is described as a genuine cognitive failure, not just an emotional one. One of Sufism’s earliest self-descriptions was ‘ilm al-qulub — “the science of hearts.”
This isn’t purely a premodern framing. A 2026 review in the cardiac-science literature surveys neurocardiology, cardioception, and psychophysiology research suggesting the heart’s role in cognition and emotional regulation is closer to what the Qur’anic vocabulary described than to a simple mechanical pump — evidence converging, from an entirely different direction, on a similar picture. Source: Ahmed S. BaHammam, “The Qur’anic Heart and Converging Evidence from Contemporary Cardiac Science: From Qalb to Cardioception” (2026), peer-reviewed medical-journal narrative review.