The Material of the System

5. The three pneumata

Galen (2nd c. CE) organises the body around three levels of function, each with its own centre, its own network, and its own pneuma.

The logic of the scale

Notice that it is a scale of refinement. Food becomes chyle in the liver (coarse), chyle becomes warm blood in the heart (finer), blood is worked in the brain into psychic pneuma (finest).

And it is a scale of voluntariness. The first level you do not control at all. The second partially and indirectly. The third directly.

This is not a theoretical detail — it is the map of what you can grasp. The whole practice of Part E rests here: you work where you have a handle, and you wait for the rest to follow.

The honest note

The tidy table of the “three pneumata” is partly later systematisation. Galen himself expresses explicit doubt about whether a physikon pneuma even exists — for him, the certainly existing one is the psychic, and with less certainty the vital. The clean triad owes more to his commentators than to him.

The fact that we know this is itself owed to him: he was honest enough to record his uncertainty — and that, ironically, is his most modern feature.

6. Pepsis: the central function

πέψις pepsis — from πέσσω pessō, to cook, to ripen. The same word is used for food in the stomach, for fruit ripening on the tree, and for an abscess “ripening” before it bursts.

It does not mean “breakdown”. It means cooking, conversion of the raw into the digestible. And the central metaphor is heat: the body has an innate heat (ἔμφυτον θερμόν emphyton thermon), and this is what cooks.

The three pepseis

The system does not stop at the stomach:

1. First pepsis — stomach/intestines. Food becomes chyle.
2. Second pepsis — liver. Chyle becomes blood and humours.
3. Third pepsis — in the tissues themselves. Blood becomes flesh — it is actually assimilated.

And at each stage, there is a residue: περιττώματα perittōmata (literally “the superfluous”). Sweat, urine, bile, phlegm — all residues of digestions.

Why this is the really useful chapter

Because it changes the question.

It is not enough what you put in. What matters is what the system can cook.

The same food, two people, two completely different outcomes — depending on the state of the innate heat. And there is a clear classical diagnosis of ἀπεψία apepsia (indigestion): heaviness after food, belching, bad odour, fogginess, tongue coating, morning sluggishness.

The instruction that follows is counter-intuitive to a modern mind: when digestion is weak, the solution is not better food — it is less food. The Hippocratic rule puts it savagely: the more you feed an impure body, the more you harm it.

And it extends. The same logic applies explicitly to recovery, to fatigue, and — in the ascetic branch of chapter 15 — to impressions. Whatever enters and is not digested, settles.

7. The four qualities: hot, cold, dry, wet

Chapter 4 showed what collapsed in the humoral theory. This chapter keeps the part that works: the four qualities as a language of description.

Two pairs, four axes. And the key point: they are relational. Nothing is hot in itself — it is hotter relative to something. Galen insists on this: the “hot” of a drug is always judged relative to the krasis of the one taking it.

The therapeutic principle

τὰ ἐναντία τῶν ἐναντίων ἰήματα — “opposites are the cures of opposites”.

This is the central allopathic principle, and its directly applicable generalisation is simple: if you have excess, go toward the opposite — gently.

The most useful diagnosis

The two axes are often confused, and the distinction changes the intervention:

• Dry/hot — you feel “burned up”. Tension, choppy breath, irritability → you need cool, moist, slow, quiet.
• Wet/cold — you feel “heavy”. Sluggishness, fogginess, difficulty starting → you need movement, warmth, lightness.
• Dry/cold — you feel “empty and tight”. Anxiety, insomnia, joint creaks, cold extremities → you need warmth and nourishment and rhythm. This is the most misread: it looks like low energy and is given the wrong treatment (stimulants, intensity), which makes it worse.

This is not a diagnosis. It is a vocabulary. And vocabulary is the first thing missing when you try to observe a state: if you have no words, you cannot see differences.

8. Dynamis, energeia, hexis

Three Aristotelian terms that are at the core, and all three have been distorted in modern Greek — and in English translation.

δύναμις dynamis — potentiality

To be able, without doing it now. The seed has the dynamis of the tree. The sleeper has the dynamis to see.

ἐνέργεια energeia — being-in-operation

From ἐν + ἔργον en-ergon, “being-at-work”. It does not mean “energy” in the physical sense — the translation of energy by this word is a 19th-century borrowing and has caused enormous confusion. Energeia is potentiality in act: the eye that is seeing right now.

ἕξις hexis — possession, settled disposition

From ἔχω echō, “to have”. A stable disposition that you have acquired and now possess. In Modern Greek it survives as exi (“habit”), but it is stronger: not simply what you do often, but what you have become able to do without struggle.

Why this may be the most practical chapter of the text

Because it answers the question “how does one change?” — and the answer is clear and unpleasant:

Hexis is built only by repeated acts. Not by understanding, not by intention, not by intensity.

Aristotle says this explicitly for virtue: we become just by doing just things. We do not do just things because we are just. The order is the reverse of what we assume.

And medicine uses the same terms for the body:

• εὐεξία euexia — good hexis. The body that has acquired good condition.
• καχεξία cachexia — bad hexis. The term survives almost unchanged as a medical term today.

The consequence for practice: health and capacity are not things you have or acquire at some point. They are states maintained by repeated function — and they decay the moment the function stops. There is no attainment. There is only maintenance.

And the other half: the small, repeatable act beats the large, non-repeatable one. Always. This is not consolation for the weak — it is the mechanical conclusion.