1911 Encyclopædia Britannica/Hippasus of Metapontum
HIPPASUS OF METAPONTUM, Pythagorean philosopher, was one of the earliest of the disciples of Pythagoras. He is mentioned both by Diogenes Laërtius and by Iamblichus, but nothing is known of his life. Diogenes says that he left no writings, but other authorities make him the author of a μυστικὸς λόγος directed against the Pythagoreans. According to Aristotle (Metaphysica, i. 3), he was an adherent of the Heraclitean fire-doctrine, whereas the Pythagoreans maintained the theory that number is the principle of everything. He seems to have regarded the soul as composed of igneous matter, and so approximates the orthodox Pythagorean doctrine of the central fire, or Hestia, to the more detailed theories of Heraclitus. In spite of this divergence, Hippasus is always regarded as a Pythagorean.
See Diogenes viii. 84; Brandis, History of Greek and Roman Philosophy; also Pythagoras.