Valentine Heart

The Stoics taught that the heart was the seat of the soul.
The Roman physician Galen located the seat of the passions in the liver, the seat of reason in the brain, and considered the heart to be the seat of the emotions. While Galen's identification of the heart with emotion were proposed as a part of his theory of the circulatory system, the heart has continued to be used as a symbolic source of human emotions even after the rejection of such beliefs.
These themes were reiterated in the European Middle Ages.