The term 'solid' occupies a strikingly diverse range of positions across the depth-psychology corpus, moving between cosmological geometry, psychodynamic structure, alchemical substance, and phenomenological selfhood. In the Platonic tradition, as mediated through the Timaeus and Cornford's commentary, 'solid' designates the three-dimensional regular figures—pyramid, cube, octahedron, icosahedron, dodecahedron—understood as the elemental building-blocks of physical reality, where solidity names both material density and formal stability. The I Ching tradition, as rendered by Ritsema-Karcher and Huang, deploys 'solid' as the translation of KANG, the quality of unbroken yang lines: firmness, persisting force, creative tension held against the yielding or supple. This polarity constitutes a field of psychic movement rather than a mere physical description. In the Buddhist-psychological register, Trungpa and Welwood interrogate the ego's compulsion to experience itself as a 'solidified' entity—a reification of open, processual awareness into a thing-like self. Hillman's alchemical psychology employs 'solid' to denote the hard lunar mind capable of granting definition to the opus. Descartes' commentators distinguish 'solid' bodies from 'subtle' ones in the context of mind-body debates. Across these registers, 'solid' marks a persistent tension: between form as ground and form as imprisonment, between creative stability and ontological illusion.
Confused mind is inclined to view itself as a solid, on-going thing, but it is only a collection of tendencies, events.
Trungpa identifies the ego's self-reification as the primary psychological error: the mistaking of a fluid, conditional process for a solid, persisting entity.
, Cutting Through Spiritual Materialism, 1973thesis
We would like to possess the same kind of solidity that we tend to perceive in the Other... Yet the very fact that we can take things into us and let them affect us... means that we ourselves are not solid, but rather empty like a mirror.
Welwood argues that the envied solidity of the Other is a projection that obscures the genuine openness constituting consciousness, inverting the Sartrean reading of en-soi as more real than pour-soi.
, Toward a Psychology of Awakening Buddhism, Psychotherapy,, 2000thesis
every sort of body possesses solidity, and every solid must necessarily be contained in planes; and every plane rectilinear figure is composed of triangles
Plato grounds his cosmological physics in the axiom that solidity—three-dimensionality contained by planes—is the fundamental property of all bodily being, reducing it to geometry.
, Timaeus, -360thesis
Solid, KANG: quality of the whole lines; firm, strong, unyielding, persisting. Stimulate, SHUO: rouse to action and good feeling... Supple Treading solid indeed.
Ritsema and Karcher define 'Solid' as the technical term for unbroken yang lines in the I Ching, designating a quality of unyielding creative persistence that stands in dynamic tension with the supple or yielding.
, I Ching: The Classic Chinese Oracle of Change, 1994thesis
Solid[and]Supple, KANG JOU: field of creative tension between the whole and opened lines and their qualities; field of psychic movement.
The I Ching concordance establishes Solid-and-Supple as a paired polarity constituting a 'field of psychic movement,' not a static opposition but a dynamic creative ground.
, I Ching: The Classic Chinese Oracle of Change, 1994thesis
it is the hard lunar mind, solid in the realization of its imaginative forms, which allows gold to be hammered into specific shape and take on definition.
Hillman identifies 'solid' with the hard lunar intelligence in alchemical psychology—the capacity of the silver psyche to give definition and workable form to the more precious but malleable gold.
, Alchemical Psychology, 2010supporting
there is just a solidified version of that color; and the color becomes captured color, and the energy becomes captured energy, because we have solidified the whole space and turned it into 'other.'
Trungpa extends the critique of solidity to perception itself: the skandhic process solidifies open perceptual energy into fixed objects, creating the illusion of a separable 'other' that then anchors the ego.
, Cutting Through Spiritual Materialism, 1973supporting
Owing to the size and uniformity of its particles metal is set hard, or solid (n8n1Jy6~). Melting begins when fire particles from outside penetrate into
Cornford's commentary on the Timaeus explains metallic solidity as a function of particle size and uniformity—large, uniform icosahedra pack tightly, producing hardness that fire dissolves by penetrating the structure.
, Plato's cosmology the Timaeus of Plato, 1997supporting
Solid 12 24 60 24 48 120 GRADE A Elements ' Equilateral iz: composed of 2 elements 4 8 20 GRADE B Solid Equilateral face~ composed
Cornford's tabulation of the regular solids across grades demonstrates that Plato's elemental theory assigns different sizes of solid to each primary body, enabling their mutual transformation through triangular decomposition.
, Plato's cosmology the Timaeus of Plato, 1997supporting
To earth let us assign the cubical figure; for of the four kinds earth is the most immobile and the most plastic of bodies. The figure whose bases are the most stable must best answer that
Plato assigns the cube to earth precisely because the cube's square bases are maximally stable, linking the quality of solidity to immobility and plasticity as complementary rather than contrary properties.
, Plato's cosmology the Timaeus of Plato, 1997supporting
the fusile kind, being formed of large and uniform particles, is more stable than the other, and is heavy and compact by reason of its uniformity... this dissolution of the solid masses is called melting
Plato's account of water's fusile variety demonstrates that solidity is a function of particle uniformity and size, and that melting names the dissolution of solid structure by fire's intervention.
, Timaeus, -360supporting
for Gassendi there is a key distinction between two kinds of body: solid (crassum) and subtle (tenue). The human body, as a set of limbs and organs, would be an example of the former
Gassendi's distinction between solid (crassum) and subtle (tenue) bodies in his objections to Descartes introduces a materialist typology within which even the soul must be located, challenging Cartesian dualism.
, Meditations on First Philosophy, 2008supporting
He begins to understand that he himself is making the walls solid, that he is imprisoning himself through his ambition.
Trungpa locates the construction of psychological imprisonment not in external conditions but in the ego's own projective activity, which solidifies boundaries that are in reality permeable.
, Cutting Through Spiritual Materialism, 1973supporting
Plato now proceeds to build the four regular solids. He begins with the construction of the equilateral triangular face which is common to the pyramid, the octahedron, and the icosahedron.
Cornford traces Plato's constructive method for the regular solids, showing how the shared triangular face links three of the four primary bodies and enables their mutual transformation.
, Plato's cosmology the Timaeus of Plato, 1997supporting
by 'planes' and 'solids' Plato certainly meant square and solid numbers respectively, so that the allusion must be to the theorems established in Eucl. viii, 11, 12
Cornford interprets Plato's use of 'solids' in the mathematical context as referring to solid numbers (cubes), situating the geometric meaning within a broader Pythagorean arithmetic framework.
, Plato's cosmology the Timaeus of Plato, 1997aside
the solid line at the fifth place... Confucius's Commentary on the Decision says, 'The firm is at the right place and properly corresponds. It accords with the time.'
Huang's commentary illustrates the I Ching's situational reading of solid (yang) lines: solidity is appropriate or inappropriate depending on positional and temporal context, not as an absolute value.
, The Complete I Ching: The Definitive Translation, 1998aside
The solid line at the second place is a yang element at a yin place—firm, strong, central. It is the only firm element in the lower gua and is responsible for enlightening and educating all the yin elements.
Huang demonstrates that a single solid line occupying a yin position carries particular pedagogical and moral authority, bearing responsibility for the development of surrounding yielding elements.
, The Complete I Ching: The Definitive Translation, 1998aside