The pineal gland as the seat of the soul (René Descartes): History of reception, enlightenment, and consequences of a famous error

René Descartes (1596-1650) was a brilliant thinker whose ideas are still reflected upon today. The Cartesian view that the pineal gland is the seat of the soul was criticized early on by Thomas Willis, Baruch Spinoza, Gottfried Wilhelm Leibniz, and Immanuel Kant, among others. Nevertheless, this historical error is still being propagated today: Helena Blavatsky supplemented this in 1888 with so-called ancient Indian knowledge about chakras, and Rudolf Steiner saw the human link to cosmic energies in the pineal calcite deposits in 1922/1923. These ideas can also be found in current medical studies. In this study, these sources are critically discussed transculturally in the context of current anatomical, physiological, and evolutionary biological knowledge.