The Lagoon: How Aristotle Invented Science

by Armand Marie Leroi

Where is the soul located? The Aristotelian answer is ‘everywhere’ and ‘nowhere’. A creature’s soul is, after all, not a physical object but the sum of its functional features. That truism, however, does not preclude the possibility that some organ or other is particularly important in its regulatory functions. In blooded animals – vertebrates – Aristotle supposes that organ is the heart. This may strike us as an odd choice: why not the brain? But that’s easily answered: the soul’s first job is nutrition, and that’s obviously no job for the brain. Very well – but what has the heart to do with nutrition? Everything, replies Aristotle. This is where his physiology becomes strange. To be sure, insofar as nutrition is carried in the blood, the cardio vascular system must somehow be involved, but Aristotle puts the heart front and centre in his nutritional physiology. He thinks that it is the main site of concoction; in fact the ‘boiling’ action of concoction is what keeps the heart in motion. The heart is the main site of concoction because it is also the site of the ‘internal fire’. We think that it’s a pump; he thinks it’s a chemical reactor. He calls it the ‘citadel of the body’ and says it has ‘supreme control’.