arts and sciences (2005)
Richtlinien und Lehrpläne für die Sek. 2 in NRW - Philosophie (1981)
Habermas' three validity claims (subjective truthfulness of I, cultural justness of we, and objective truth of its) (1981)
the Herrmann Brain Dominance Instrument (1978)
Keirsey's four temperaments (1978)
Karl Popper's 'three worlds' (subjective, cultural, and objective) (1972)
mechatronics (1969)
Myers's cognitive function types (1958)
Hans Eysenck's Dimensions of Personality (1947)
the AGIL Paradigm (1956)
Piaget's stages of cognitive development (1951)
Gurdjieff and Ouspensky's Law of Three (1950)
William Moulton Marston's DISC-Theory (1928)
Jung's Compass of the Soul (1921)
Steiner (Thinking, Feeling, Willing, three streams of evolution, and the Three Fold Commonwealth) (1913)
the four lobes of the cerebral cortex
Kant's three critiques (1790)
the coordinate system (1637)
Hildegard von Bingen (12th century)
Galen's four temperaments
Plato's the Good, the True and the Beautiful (360 bc)
the Three Jewels (500 bc)
the Medicine Wheel of Native American spirituality
