The Lagoon: How Aristotle Invented Science

by Armand Marie Leroi

have been talking about the soul all along. The system that I have described – the structure of the metabolic network – is the nutritive soul, or at least a part of it. The ends to which a creature puts its nutrients, how much of each kind of uniform part it will make and when and where it will do so, its growth, its reproduction and its death – all of these depend on the organization of metabolism and all depend, Aristotle tells us, on the nutritive soul. Yet there is more to the nutritive soul than this: Some think the fire itself is the main cause of nutrition and growth. It’s not – the soul is; though it may be a contributory factor. Fires will always grow so long as there’s fuel but the size and growth of all naturally composed (i.e. living) things is limited and defined: this is the job of the soul not the fire, of defining characteristics not matter. We must imagine Aristotle sitting in front of a hearth (as Heraclitus was said to do), staring into the fire, occasionally poking it, thinking about the fire that rages inside him, that keeps him alive, that permits his thoughts to flow apparently without cease, devouring the world. ‘Fire is always coming into being and flowing like a river’ – how very true. But no fire can rage unchecked for ever lest it consume itself. All fires must be fuelled, stoked, damped – regulated – if the tenuous flame of existence is to be maintained.