Philosopher, Mathematician (c.500 BC)

Hippasus of Mentapontus was a Pythagorean philosopher, one of Pythagoras’ first students initiated into Pythagoreanism and founder of the Mathematical Department of Pythagoras’ School.

He was active during the first 30 years of the 6th century BC and is considered as one of the oldest Pythagorean philosophers, as well as Pythagoras’ first assistant. While himself Pythagorean, Hippasus’ teachings differed slightly from those of Pythagoreans. For instance, he believed that the beginning of the world is matter (fire) rather than immaterial (numbers). He wrote a book Secret Logos, which he published under the name of Pythagoras, containing his philosophy. Only fragments of his book survive today.

As a mathematician, Hippasus is the discoverer of irrational numbers, infinite decimals with no indefinitely repeating digits. Furthermore, he discovered that the ratio of a side of a pentagon to the diagonal of a pentagon is equal to an irrational number and that the length of an isosceles’ triangle shorter side is an irrational number if the length of the two equal sides is a whole one.

Not surprisingly, Hippasus was also an inventor. He is credited as having constructed containers with varying amounts of water each, including metal plates of varying thickness with which he made acoustic experiments on the harmony of sound. In Pythagoras’ school, Hippasus was not only the founder the department of mathematics, but also the founder of the “cycle of acoustic scientists”, a body tasked with conducting experiments on sound and music using the aforementioned inventions. The body studied the relationship between music and mathematics.

According to some ancient writers, Hippasus was accused of publicizing secret Pythagorean knowledge to outsiders or uninitiated people, which was strictly forbidden by Pythagorean oath and was subsequently persecuted. Nevertheless, he is held on high regards by modern day historians of science.


  1. Georgakopoulos, Konstantinos. Ancient Greek Scientists. Georgiades: Athens, 1996. Print.
  2. Σακελλαρίου, Γεώργιος. Πυθαγόρας Ο Διδάσκαλος τῶν Αἰώνων. Ἰδεοθέατρον. Ἀθῆναι: 1963. Print.
  3. “Hippasus”. Helios New Encyclopaedic Dictionary. Passas, I. Athens: 1946. Print.
  4. “Hippasus of Metapontum.” Science and Its Times: Understanding the Social Significance of Scientific Discovery. Encyclopedia.com. 23 Apr. 2019<https://www.encyclopedia.com&gt;.

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