The triangle occupies a surprisingly multivalent position within the depth-psychology corpus, functioning simultaneously as cosmological element, psychological symbol, geometric archetype, and epistemological figure. Plato's Timaeus establishes the foundational valence: triangles are the irreducible elements of plane figures, and through them the four elements receive their formal constitution—fire, air, water, and earth each assigned a regular solid whose faces decompose into two fundamental triangular forms. This ontological grounding reverberates through later psychological thought. In Jungian and post-Jungian writing, the triangle accrues specifically trinitarian significance: Edinger reads the triangular image as representing the dynamic, threefold principle of thesis-antithesis-synthesis that breaks open static, circular completeness. The AA symbol—a triangle inscribed within a circle—links Wilson's recovery theology to Jung's mandala work and alchemical traditions of squaring the circle. Nichols, reading Tarot numerology, finds the triangle implicit in the six-pointed star as the union of heaven-pointing and earth-pointing apices. Descartes deploys the triangle repeatedly as the paradigm case for essence, existence, and clear-and-distinct perception. Merleau-Ponty uses it to contest formalist essentialism: the triangle's truth is not analytic but phenomenological, dependent on its Gestalt as drawn. The term thus traverses cosmology, number mysticism, trinitarian theology, phenomenology, and symbolic amplification, making it one of the more richly layered geometric concepts in the tradition.
In the library
14 passages
To the triangle the patient associated the trinitarian image of God… the triangle. I understand this dream as referring to the break up of an original state of uroboric wholeness… by means of a three-fold dynamic process represented by the triangle.
Edinger interprets the triangle as the psyche's symbol for the trinitarian dynamic principle—thesis, antithesis, synthesis—that disrupts static ego-Self identity and initiates developmental time.
Edinger, Edward F., Ego and Archetype: Individuation and the Religious Function of the Psyche, 1972thesis
Wilson introduced a symbol for A.A. of a triangle within a circle, accompanied with the words Unity, Service, and Recovery inscribed along the edges of the triangle. This symbol is highly correlated to the mandalas that Jung noticed emerging spontaneously in the drawings of his patients who had achieved a certain level of wholeness.
Peterson links Wilson's AA triangle-within-circle to Jung's mandala symbolism and alchemical squaring-of-the-circle, positioning the triangle as an emblem of integrated wholeness in recovery psychology.
Peterson, Cody, The Shadow of a Figure of Light, 2024thesis
every plane rectilinear figure is composed of triangles; and all triangles are originally of two kinds, both of which are made up of one right and two acute angles
Plato establishes the triangle as the irreducible geometric element from which all plane figures—and thus all material bodies—are ultimately constructed.
the triangle, as the surface contained by the minimum number of straight lines, is 'assumed' as the irreducible 'element' of all such figures… If planes can be constructed of triangles, triangles themselves can be constructed of lines, and lines can be expressed as numbers.
Cornford's commentary shows that Plato treats the triangle as the ontological bridge between geometric solids and number, revealing a hierarchy of principles underlying physical reality.
Plato, Plato's cosmology the Timaeus of Plato, 1997thesis
The construction which enables the conclusion to be reached is not really contained in the essence of the triangle, but merely possible when that essence serves as a starting point… these steps are possible only if I consider the triangle itself as it is drawn on the paper… in short its Gestalt.
Merleau-Ponty uses the triangle as a phenomenological counter-example to formalist essentialism, arguing that geometric necessity depends on embodied perception of the figure's Gestalt, not on analytic definition.
Merleau-Ponty, Maurice, Phenomenology of Perception, 1962thesis
Six is also the number of completion… Symbolically, six is pictured as a six-pointed star. This star is composed of two triangles, one with its apex pointing up toward heaven and the other with its apex pointi
Nichols identifies the two interlocked triangles of the hexagram as symbols of cosmic completion and the union of heavenly and earthly principles, embedded in Tarot numerological symbolism.
Nichols, Sallie, Jung and Tarot: An Archetypal Journey, 1980supporting
although perhaps we could accept that in the concrete a triangle is a substance having a triangular shape… we cannot, however, in the same way, clearly understand a triangle the square of the base of which is equal to the sum of the sides, without at the same time realizing that it is right-angled.
Descartes employs the triangle as the canonical example for the relationship between essence and necessary properties, distinguishing between what can and cannot be clearly conceived in isolation.
Descartes, René, Meditations on First Philosophy, 2008supporting
omnipotence can no more be separated from God's existence than having angles equal to two right angles can be separated from the essence of a triangle
Descartes uses the necessary properties of a triangle as an analogy to argue that existence cannot be separated from the divine essence, making the triangle his paradigm for necessary conceptual entailment.
Descartes, René, Meditations on First Philosophy, 2008supporting
I clearly and distinctly understand that this triangle is right-angled, even though I do not understand whether the square of its base is equal to the square of the other two sides. Therefore God can at least produce a right-angled triangle, the square of the base of which is not equal to the square of the sides.
Descartes tests the limits of clear-and-distinct perception through the triangle's geometric properties, using it to probe the relationship between conceivability and metaphysical possibility.
Descartes, René, Meditations on First Philosophy, 2008supporting
He begins with the construction of the equilateral triangular face which is common to the pyramid, the octahedron, and the icosahedron. The 'element' is the half-equilateral, 'whose hypotenuse is double of the shorter side in length'.
Cornford reconstructs how Plato's two elementary triangles—the half-equilateral and the half-square—serve as the constructive units for all four regular solids assigned to the elements.
Plato, Plato's cosmology the Timaeus of Plato, 1997supporting
216 is the cube of 6, and also the sum of 3 cubed, 4 cubed, 5 cubed, the numbers 3, 4, 5 representing the Pythagorean triangle, of which the sides when squared equal the square of the hypotenuse
The Republic commentary situates the Pythagorean right triangle at the heart of Plato's number mysticism, linking it to cycles of generation and the musical scale.
the construction 'in each case originally produced its triangle not of one size only, but some smaller, some larger'
Cornford clarifies that Plato's elementary triangles exist in multiple sizes, which explains the plurality of grades within each primary body and the variety of their transformations.
Plato, Plato's cosmology the Timaeus of Plato, 1997supporting
when he is asked whether a certain triangle is capable of being inscribed in a certain circle… will reply: 'I cannot tell you as yet; but I will offer a hypothesis which may assist us in forming a conclusion'
In the Meno, the triangle-in-a-circle problem serves as the model for hypothetical reasoning in geometry, which Socrates then transfers to the epistemological question of whether virtue can be taught.
The Eye of the Holy Spirit, here shown at the summit of a Pyramid of Creation, is a counterpart of the Eye of Vishnu mentioned in the Indian tale of the 'Humbling of Indra'.
Campbell reads the triangular pyramid on the Great Seal as a mythological symbol of creation and divine vision, connecting it to comparative religious iconography rather than psychological analysis proper.
Campbell, Joseph, The Inner Reaches of Outer Space: Metaphor as Myth and as Religion, 1986aside