Across the depth-psychology corpus, 'fluid' operates simultaneously as a cosmological element, a physiological substrate, a psychological metaphor, and an ontological principle. The term carries at least four distinct registers that often interpenetrate. In archaic Greek physiology, as reconstructed by Onians, bodily fluids — synovial fluid, cerebro-spinal fluid, seed, sweat — are identified as the very 'stuff of life', the vehicle of the aion and the seat of psychic vitality; to lose fluid is to lose vigour, intelligence, and generative power. In Platonic cosmology, following the Timaeus, water as the paradigmatic fluid occupies a middle register of the elemental hierarchy, its mobility and fusibility explained geometrically and deployed in elaborate hydraulic metaphors for digestion, nutrition, and psychic circulation. A third register, prominent in McGilchrist, treats fluidity as an ontological condition: reality itself flows, resistance to flow generates turbulent creativity, and the apparently solid is revealed as process. Finally, in alchemical depth-psychology (Edinger), the dissolution of the psyche into a molten, liquid-flowing state is the mark of psychic quality and openness — the solutio — echoing Taoist water imagery. The central tension running through all registers is between fixity and flux: whether fluidity bespeaks vital health or dangerous dissolution, creative openness or loss of form.
psychic quality is indicated by its ability to soften, to melt into a liquid flowing state.
Edinger argues, via alchemical solutio symbolism, that the capacity to become fluid is itself the criterion of psychological nobility and value.
, Anatomy of the Psyche: Alchemical Symbolism in Psychotherapy, 1985thesis
sweat, the pale liquid coming out of the flesh, and synovial fluid, the liquid in the joints, are one and are the stuff of strength, vigour
Onians demonstrates that archaic Greek physiology unified sweat, synovial fluid, cerebro-spinal fluid, and seed as interchangeable expressions of a single life-sustaining substance.
, The origins of European thought about the body, the mind,, 1988thesis
sweat, the pale liquid coming out of the flesh, and synovial fluid, the liquid in the joints, are one and are the stuff of strength, vigour, appears... to have been part of the earliest Greek physiology
This parallel passage reinforces Onians's central claim that multiple bodily fluids were considered ontologically identical as vehicles of psychic and physical force.
, The origins of European thought about the body, the mind,, 1988thesis
When the fluid blood rushes away, the bubbling air rushes in.... When the blood leaps up, the air is breathed out again.
Padel illustrates, via Empedocles, that fluid and breath are interchangeable in the same bodily channels, making fluid the dynamic medium through which inner psychic states are regulated.
, In and Out of the Mind Greek Images of the Tragic Self, 1994thesis
original sense of fluid for cdcbv... It flows away in tears.
Onians traces how aion originally designated a life-fluid whose loss through tears or wounds constitutes the departure of vitality, prefiguring later psychological concepts of psychic energy.
, The origins of European thought about the body, the mind,, 1988thesis
when fire gets in and dissolves the particles and destroys the uniformity, it has greater mobility, and becoming fluid is thrust forth by the neighbouring air and spreads upon the earth
Plato's Timaeus presents fluidity as the cosmological consequence of dissolution — fire breaking down uniform structure to produce mobile, spreading matter — establishing the philosophical archetype for alchemical solutio.
, Timaeus, -360thesis
No obstruction in the path of a flow is required for it to become turbulent; any inequality in speed or viscosity within the flow itself can lead to turbulence.
McGilchrist uses fluid dynamics to argue that turbulence — and hence creative complexity — arises from internal tensions within flow itself, not merely from external obstacles.
, The Matter With Things: Our Brains, Our Delusions and the Unmaking of the World, 2021supporting
No obstruction in the path of a flow is required for it to become turbulent; any inequality in speed or viscosity within the flow itself can lead to turbulence.
A parallel passage reinforcing McGilchrist's ontological argument that inner inequality within fluid motion is the generative engine of natural complexity.
, The Matter with Things: Our Brains, Our Delusions, and the Unmaking of the World, 2021supporting
even what we conceive to be the 'solid' parts of cells are actually flows.
McGilchrist collapses the solid/fluid distinction at the cellular level, arguing that apparent solidity is a provisional form of ongoing flow.
, The Matter With Things: Our Brains, Our Delusions and the Unmaking of the World, 2021supporting
Stability in the experiential world is always stability provided by a form through which things continue to flow: 'As they step into the same rivers, other and still other waters flow upon them'
McGilchrist deploys Heraclitean river imagery to argue that all stability is dynamic, a form maintained by continuous flowing, not by stasis.
, The Master and His Emissary: The Divided Brain and the Making of the Western World, 2009supporting
Schelling clearly intuited that water was a potent metaphor or symbol for the nature of reality, as indeed it is in Oriental philosophy, especially Taoism, which constantly recurs to the image of flowing water.
McGilchrist locates flowing water as a cross-cultural philosophical symbol for the dynamic, self-equilibrating nature of reality, linking Schelling's Naturphilosophie to Taoist thought.
, The Matter With Things: Our Brains, Our Delusions and the Unmaking of the World, 2021supporting
Schelling clearly intuited that water was a potent metaphor or symbol for the nature of reality, as indeed it is in Oriental philosophy, especially Taoism, which constantly recurs to the image of flowing water.
Parallel passage establishing the water-as-reality metaphor as central to McGilchrist's process-ontological framework.
, The Matter with Things: Our Brains, Our Delusions, and the Unmaking of the World, 2021supporting
Water, again, admits in the first place of a division into two kinds; the one liquid and the other fusile.
Cornford's commentary on the Timaeus articulates Plato's systematic differentiation of fluid states — liquid versus fusible — as a geometry-based account of matter's mobility.
, Plato's cosmology the Timaeus of Plato, 1997supporting
Plato's main concern is with the hydraulics of his irrigation system.
Cornford identifies Plato's physiological account of digestion and respiration as fundamentally hydraulic, treating bodily fluid circulation as the template for understanding life processes.
, Plato's cosmology the Timaeus of Plato, 1997supporting
The life-fluid was, as we saw, concentrated particularly in the head, the seat of the genius.
Onians identifies the life-fluid as localized in the head and associated with the genius, connecting fluid with divine vitality and the seat of personal fate.
, The origins of European thought about the body, the mind,, 1988supporting
the fluid or liquefiable content of the joint, its true function
Onians traces beliefs about the fluid in the knee-joint as the generative substance underlying both physical vigour and cosmogonic power in archaic Indo-European thought.
, The origins of European thought about the body, the mind,, 1988supporting
every cell in the body is bathed in the extracellular fluid... it is rich in ions—electrically charged atoms such as sodium, potassium, and chloride.
Kandel describes the extracellular fluid as the ionic medium through which electrical signalling in the nervous system is made possible, grounding psychological function in fluid chemistry.
, In search of memory the emergence of a new science of mind, 2006aside
DMT would also benefit from the small distances, only millimeters wide, between the pineal and important brain structures. It could diffuse directly onto these brain sites by way of the cerebrospinal fluid
Strassman proposes cerebrospinal fluid as the pathway for endogenous DMT to reach the brain's visionary and emotional centres, making fluid the vehicle for transpersonal experience.
, DMT: The Spirit Molecule, 2001aside
turbulent motion of fluids... Richard Feynman described turbulence as the most important unsolved problem of classical physics.
McGilchrist invokes fluid turbulence as emblematic of the deepest unresolved complexity in nature, situating fluid dynamics at the frontier of scientific understanding.
, The Matter With Things: Our Brains, Our Delusions and the Unmaking of the World, 2021aside