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{{Short description|Symbol of ten points laid in four rows}}thumb|200px| The tetractysThe tetractys (), or tetrad,{{citation|url=weblink|title=The Theosophical Glossary|page=302|publisher=Forgotten Books |isbn=9781440073915}} or the tetractys of the decadBOOK, 36, Eduard Zeller, Eduard Zeller, Outlines of the History of Greek Philosophy, 13, is a triangular figure consisting of ten points arranged in four rows: one, two, three, and four points in each row, which is the geometrical representation of the fourth triangular number. As a mystical symbol, it was very important to the secret worship of Pythagoreanism. There were four seasons, and the number was also associated with planetary motions and music.{{citation|url =https://books.google.com/books?id=DQpSA4CEnIwC| title = Pythagoras: pioneering mathematician and musical theorist of Ancient Greece| author = Dimitra Karamanides| publisher = The Rosen Publishing Group|year= 2005 |pages=65| isbn = 9781404205000}}

Pythagorean symbol

1. The first four numbers symbolize the musica universalis and the Cosmos as:
   • Monad – Unity
   • Dyad – Power – Limit/Unlimited (peras/apeiron)
   • Triad – Harmony
   • Tetrad – KosmosThe Pythagorean Sourcebook and Library by Kenneth Sylvan Guthrie
2. The four rows add up to ten, which was unity of a higher order (The Dekad).
3. The Tetractys symbolizes the four classical elements—air, fire, water, and earth.
4. The Tetractys represented the organization of space:
   • the first row represented zero dimensions (a point)
   • the second row represented one dimension (a line of two points)
   • the third row represented two dimensions (a plane defined by a triangle of three points)
   • the fourth row represented three dimensions (a tetrahedron defined by four points)

A prayer of the Pythagoreans shows the importance of the Tetractys (sometimes called the "Mystic Tetrad"), as the prayer was addressed to it.The Pythagorean oath also mentioned the Tetractys: It is saidIntroduction to Arithmetic – Nicomachus{{citation|url=https://books.google.com/books?id=q-1o3tUGcXMC&q=tetraktys+diatessaron&pg=PA66|title=The Musical Order of the World: Kepler, Hesse, Hindemith-Siglind Bruhn|isbn=9781576471173|last1=Bruhn|first1=Siglind|year=2005|publisher=Pendragon Press }}{{citation|url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0063:entry=musica-cn&highlight=pythagorean%2Cpythagoras|title=A Dictionary of Greek and Roman Antiquities(1890) – William Smith, LLD, William Wayte, G. E. Marindin, Ed.}} that the Pythagorean musical system was based on the Tetractys as the rows can be read as the ratios of (diatessaron|4:3) (perfect fourth), 3:2 (perfect fifth), (Pythagorean interval#Interval table|2:1) (octave), forming the basic intervals of the Pythagorean scales. That is, Pythagorean scales are generated from combining pure fourths (in a 4:3 relation), pure fifths (in a 3:2 relation), and the simple ratios of the unison (unison|1:1) and the octave (octave|2:1). Note that the diapason, 2:1 (octave), and the diapason plus diapente, 3:1 (compound fifth or perfect twelfth), are consonant intervals according to the tetractys of the decad, but that the diapason plus diatessaron, 8:3 (compound fourth or perfect eleventh), is not.{{citation|url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A2008.01.0386%3Asection%3D14|title=Plutarch, De animae procreatione in Timaeo – Goodwin, Ed.(lang.:English)}}{{citation|url=https://books.google.com/books?id=ehDG5mGUYAMC&q=tetraktys+diatessaron&pg=PA56|title=Sacred Architecture of London – Nigel Pennick|isbn=9781904658627|last1=Pennick|first1=Nigel|date=January 2012|publisher=Aeon Books }}

Kabbalist symbol

In the work by anthropologist Raphael Patai entitled The Hebrew Goddess, the author argues that the tetractys and its mysteries influenced the early Kabbalah.BOOK, Patai, Raphael,weblink The Hebrew Goddess, 1967, Wayne State University Press, 0-8143-2271-9, registration, - Chapter V - The Kabbalistic Tetrad A Hebrew tetractys has the letters of the Tetragrammaton inscribed on the ten positions of the tetractys, from right to left. It has been argued that the Kabbalistic Tree of Life, with its ten spheres of emanation, is in some way connected to the tetractys, but its form is not that of a triangle. The occultist Dion Fortune writes: The relationship between geometrical shapes and the first four Sephirot is analogous to the geometrical correlations in Tetraktys, shown above under #Pythagorean symbol, and unveils the relevance of the Tree of Life with the Tetraktys.

Occurrence

File:Women_Bowling_(2870338513).jpg|thumb|Ten-pin bowlingTen-pin bowlingImage:Template-Metropolitan Archbishop.svg|thumb|100px|right|Coat of arms of an archbishop of the Catholic ChurchCatholic ChurchThe tetractys occurs (generally coincidentally) in the following:

• the baryon decuplet
• an archbishop's coat of arms
• the arrangement of bowling pins in ten-pin bowling
• the arrangement of billiard balls in ten-ball pool
• a Chinese checkers board
• the "Christmas Tree" formation in association football

In poetry

In English-language poetry, a tetractys is a syllable-counting form with five lines. The first line has one syllable, the second has two syllables, the third line has three syllables, the fourth line has four syllables, and the fifth line has ten syllables.{{citation|url=weblink|title=English Syllable Counters}} A sample tetractys would look like this: The tetractys was created by Ray Stebbing, who said the following about his newly created form:

See also

• Pascal's triangle

References

{{Reflist}}

Further reading

• von Franz, Marie-Louise. Number and Time: Reflections Leading Towards a Unification of Psychology and Physics. Rider & Company, London, 1974. {{isbn|0-09-121020-8}}
• Fideler, D. ed. The Pythagorean Sourcebook and Library {{Webarchive|url=https://web.archive.org/web/20150509045621weblink |date=2015-05-09 }}. Phanes Press, 1987.
• The Theoretic Arithmetic of the Pythagoreans – Thomas Taylor

External links

• Examples of Tetractys poems

{{Ancient Greek philosophical concepts}}