The Fourth Element of the Soul in Lucretius

When we study Epicureanism, we often find that we must revisit a subject over and over again, both by ourselves and with other students of like mind, so that we can slowly assimilate when we’re being taught. In his Wall Inscription, Diogenes of Oenoanda actually mentions this process in an epistle to a friend where he mentioned that each time they discussed the doctrine of the innumerable worlds, they got a bit closer to a clearer conception of the main ideas of the doctrine.

The Epicurean conception of the soul is one of those conversations that requires revisiting. Ancient Epicureans, although they lived a pre-scientific society, were attempting to apply empirical thinking methods to the demystification of the natural, physical soul (the “psyche”). In doing this, they produced the first stirrings of neurology and non-shamanic psychology. In this essay, I will argue that Lucretius was attempting to describe the neurons and the neurological system when he expounded on the fourth component of the soul, although he confessed that the ancient Latin language lacked the words to explain what he meant. Please enjoy this short video by SoFE on the nature of the soul if you’d like a quick introduction to the subject.

The Nameless Element

In Book 3 of DRN, Lucretius presents a non-supernatural theory of the soul (psyche) based on the study of nature. After accounting for the first three elements of the soul aer, calor, and aurea (more on that later), he says:

Thus, to this point
we have found that the nature of the soul
has three parts, but these three things together
are not enough to create sensation,
since facts do not accept that any of these
could produce those motions that generate
our senses [and thoughts moving through our minds.

De rervm natvra, Liber Tertivs, Verses 325-331

He begins by saying that the previous three elements are not enough to account for all of the soul’s faculties. He then proceeds to explain what he considers to be the fourth element of the soul. This is a much more elaborate theory than what we find in Epicurus’ Epistle to Herodotus (beginning in Portion 63).

Thus, to these three substances we must add
a certain fourth nature, as well, something
that has no name at all. But there is nothing
more agile or more tenuous than it,
or made of smaller, smoother elements.
This matter first sends out through the body
those motions which activate sensations.
For since it is composed of tiny shapes,
it is the first substance stirred, and from it
heat as well as the hidden force of wind                             
acquire motion, and from that air, as well.

De rervm natvra, Liber Tertivs, Verses 332-342

We are beginning to see that this fourth element had no name in the First Century BCE when Lucretius was writing in the Latin language. Because it is needed to account for the near-instant reactions and movements that happen in our bodies, and the networks of communication between body parts that are required to account for them, it is believed to be made up of tiny, subtle, and agile particles.

It seems, from these preliminary ideas, that he is referring to the neurological system (the nerves and the brain). This is confirmed next, when we see that this fourth element accounts for pleasure and pain throughout the body.

After that everything is mobilized—
blood is roused, and then all flesh feels it, too,
and bones and marrow get it last of all,   
whether pleasure or a burning torment
of the opposite kind. And pain cannot
easily penetrate as far as this,
nor any bitter evil move within,
without all matter being shaken up,
so much so that there is no room for life,  
and through all the openings of the body
the parts of soul disperse. But generally,
a limit is set to motions, as it were,
on the surface of the body—that is why
we stay strong enough to maintain our lives.

De rervm natvra, Liber Tertivs, Verses 343-356

Lucretius surmises accurately that these particles must be inside the body and protected by the skin and other tissue from outside harm. The particles of the soul are not superficial, even if we have nerves on our skin. This is reiterated again in verse 379, where Lucretius says: “This fourth nature lies completely hidden,
far inside”.

After confessing that his native language was still incapable of communicating the nature of the psyche, but that he was willing to try to explain it, he goes on to describe the psyche as an emergent property or mixture of many elements (“many forces of one body”, verse 367). This is one of the main arguments that materialists are still making concerning the nature of sentience: it is an emergent property of bodies, and ergo complex and made up of many smaller processes.

These primary substances,
through motion of primordial elements,
move among themselves, so no single one
can be cut out, nor can its power become
set off from the rest by any space. They are,
as it were, many forces of one body.
Just as in the flesh of any creature
anywhere at all there is an odour,
a certain heat, and taste, yet from all these
a single corporeal mass is formed,
so heat, air, and hidden power of wind
create in combination one nature,
together with that active force which sends
out from itself to those three parts the start
of movements from which arise those motions
which first bring sensation to the tissues.

De rervm natvra, Liber Tertivs, Verses 363-378

In order to adhere to their empirical standards (see this essay on epilogismos), ancient Epicureans inferred by analogy about the non-evident based on that which was evident (as shown in Epicurus’ Epistle to Pythocles). Here, we see that they applied this method to the soul. Lucretius surmises that particles of the psyche must be able to touch each other (“nor can its power become set off from the rest by any space”). Otherwise, we would have to account for the quickness of movement throughout the body. As soon as we decide to move our toes, they move, but it’s difficult to account for a particle that can travel at light speed from head to toe, so the tiny cells of the soul are imagined as connected to each other and as able to communicate with each other by exchanging signals.

My view is that Lucretius is describing the neurons, although he does not have this word in his vocabulary. Neurons are the cells of the soul, and the primary elements of it in a manner of speaking, although they themselves are composed of simpler elements.

Our neurons are connected, like a network, and they work by exchanging electric signals with each other (“firing” together), and by many other chemical and electric reactions throughout the body.

The Other Elements

A bit later, Lucretius accentuates that the soul is a system or an emergent property made up of many elements.

… wind, air, and heat all combined together
throughout the limbs must act effectively—
one being more subservient to the others
or more prominent, but in such a way
that all of them seem to create one thing,
so heat and wind, without the other parts,
or the power of air all by itself,
could not separate from other portions
and abolish and dissolve sensation.

De rervm natvra, Liber Tertivs, Verses 391-399

Reference to heat (calor) as an element of the soul probably originates in the observation by primitive people that the body becomes cold and stiff upon death, and so the sentient faculties must be tied to a heat-giving process. Reference to wind or air may refer to the loss of breath upon death. Since these properties leave the body upon death, they were reasonably associated with that which makes sentience happen.

In verses 400-407, Lucretius links heat with excessive passion and rage (Philodemus explained this in his scroll On Anger, where he depicted the face becoming red with rage due to blood rushing), whereas he links the aurea (wind) element to fear. He differentiates between winds and air, referring to air as the passive, undisturbed, serene state of normal breathing (the state of ataraxia, tranquility, eustatheia), while winds represent the huffing and puffing of an anxious soul. Since he ties “winds” to fear, I believe that our modern conception of this soul faculty might be tied to the fight-or-flight faculty.

Lucretius explains that different creatures (including humans) have different combinations of these elements of the soul. This explains how some natures are more prone to anger, while others are more prone to fear, or to serenity, and also how some people have difficulty changing their initial constitution. Epicurus echoes this when he acknowledges the limits of the ethical alchemy that can be achieved from the “initial constitution” all the way the “final product” in his sermon on moral development. However, Epicurus and Lucretius both do not accept this as an excuse to avoid working on our character.

The remaining traces   
of those natures which reasoning cannot
remove from us are so slight, that nothing
stops us living a life worthy of the gods.

De rervm natvra, Liber Tertivs, Verses 343-346

One final note on the elements of the soul. When trying to imagine what conversations between the Kathegemones might have led to these ideas, it occurs to me that the Aurea element is tied to fear and to the fight-or-flight drive, and the Calor element is tied to ardent desire (including hunger, thirst) and digestion (the Ayurvedic “fire in the belly”, or the fumes of an engine that is consuming fuel, an apt metaphor for the digestive and breathing functions). They remind me of problems that sentient beings have always had to solve: the need to not be eaten and the need to eat. The Aer element reminds me of satiation, rest and digestion. If we juxtapose the logic of Darwinian evolution by natural selection to the emergence and development of these drives, we see that sentient beings could not have reproduced and passed down their genes without these drives, and therefore the “soul” functions that keep bodies alive would have been necessary emergent properties of bodies from the beginning of the history of multi-cellular life. Seen this way, it is easy to understand how the “soul” (psyche) is an emergent property of the body, co-evolved with it, emerges and dies with it.

Conclusion

Lucretius lacked the word neuron in Latin, and I was initially tempted when I wrote this essay to identify the neuron as the fourth element of the Epicurean soul, but that risks over-simplifying the matter. The most accurate English description of the fourth element is, in my view, the neurological system—with a strong emphasis on “system”.

It was probably a good idea for Lucretius to avoid coining a word in Latin for the fourth element as he did for the other three. Let us continue to mull over this subject for many years, and to get progressively closer to a fully scientific, demystified, natural account of the soul.

Further Reading:

Passages on the Soul, from Epicurus’ Epistle to Herodotus

The Concrete Self