“It is plain that the earth contains breath: I do not mean just the breath that makes it cohere and keep its parts united, which is found even in rocks and dead bodies, but I mean the life-giving breath that is vigorous and sustains everything. Unless it contained this, how could it instill breath into all those trees and all those plants that have no other source of life? How could it nourish all the different kinds of roots that go down into it in different ways — some growing near the surface, others sent deeper down — unless it contained a lot of soul to produce so many, varied plants and make them grow as they breathe and feed on it?” (Seneca, Natural Questions, “On Earthquakes”, 16.1)

He goes on to describe how this life-giving breath, the earth’s soul, flows out of the earth and how that breath sustains all the “heavenly bodies” through the “fiery aether”: “All these draw their nourishment from the earth and share it among themselves, and are obviously sustained by nothing other than the earth’s exhalation.” (16.2)

Earthquakes are caused by the breath trapped inside the earth that can’t escape, “when it is robbed of all opportunity of leaving and is obstructed on every side” (18.2).

Just as all things are nourished by this breath, so is the human body:

Our own bodies as well tremble only if some factor upsets the breath in them: when it contracts with fear, when it grows weak with old age and becomes feeble is sluggish veins, or when it is subdued by cold or diverted from its usual course by the onset of a fever. As long as it is flowing unimpaired and moving as normal, there is no trembling in the body. But when something arises that restricts its normal functioning, then it is not strong enough to tolerate what it had been able to endure while it was healthy; it grows weak and causes shaking in parts of the body that, when itself was strong, it kept firm. (18.6-7)

It’s an amazing world view to imagine that the same forces that create earthquakes is flowing through the body and causing fever and trembling.