Posted by: dacalu | 4 February 2015

Aristotle’s Vegetable Souls

This is the next installment in the long delayed series on the history of souls. The series began with a blog on the different uses of the concept through the ages. In the last few posts, I talked about Aristotle’s causes, substances, and thoughts on life.

For Aristotle, the soul was a special kind of scientific explanation. He wanted to reduce all motion in the world a set of first principles. Some authors prefer to think of them in very abstract philosophical or religious terms. I prefer to treat them as the basic rules by which we describe the way the world works, much like gravity and magnetism in modern science.

Aristotle speaks of four elements: earth, water, air, and fire. He presents them as concentric spheres, surrounded by an unchanging aether (the “fifth element”). In our realm below the moon the four elements seek their natural places; earth always sinks; fire always rises; water and air settle in between. This need not be mysterious as it matches well with modern concepts of density dependent sorting. Think of a pond with silt settling to the bottom and air bubbles rising to the top. Fire, in turn explained the movement of smoke upward through the air. Aristotle thought that one element could transform into another and that abiotic movement – what we think of as physics – was caused by the cycling of the four elements. A bit of earth would sink until it reached the sphere of earth or was transformed into water or air.

Some things just weren’t captured in this scheme. Volcanoes are easy – fire goes up. Living things were hard. Aristotle needed some further explanation for them, particularly the apparently goal directed processes of nutrition, reproduction, motion, sensation, and reason. For these, he suggests the three-fold cause or “soul.”

The Three-fold Cause

Aristotle introduces the idea that sometimes the formal cause (what a thing is, essentially), the efficient cause (what brings it about), and the final cause (where it’s going) are all the same thing. The simplest case is reproduction. What is a living thing but something that reproduces, is a copy of a parent, and works toward the end of making offspring. That comes suspiciously close to modern definitions of life based on evolution by natural selection. Reproduction is the defining feature, the cause, and the effect of life.

Aristotle thought in slightly different terms. For him the simplest case was nutrition. Remember that he saw everything as a combination of form and matter. A living thing was a form that was actively imposing itself on more matter. A living thing eats and the stuff it eats loses its original form (cookie) and takes on a new form (Sharon), despite never changing it’s matter (carbohydrates and fats). Every time you eat something, you are engaged in this process of incarnation, imposing form on matter.

The soul was not some supernatural entity that magically gave living things the power of nutrition. (Sadly it was read that way in the Renaissance.) It was the active process (energeion – in action) and achieved goal (entelecheia – in completion) of perpetuating a pattern in tangible stuff. The “vegetable soul” for Aristotle was the same thing as nutrition in action.


  1. […] thought of souls as forms travelling through time, both as patterns in space and a chemical process of […]

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