 There are only a few other assertions about the cosmology of Hippasus and most of these seem to be the result of Peripatetic attempts to classify him, such as the assertions that he makes all things from fire by condensation and rarefaction and dissolves all things into fire, which is the one underlying nature and that he and Heraclitus regarded the universe as one, (always) moving and limited in extent (DK I 109.8–10). More intriguing is the claim that he thought there was “a fixed time for the change of the cosmos” (Diogenes Laertius VIII 84), which might be a reference to a doctrine of eternal recurrence, according to which events exactly repeat themselves at fixed periods of time. This doctrine is attested elsewhere for Pythagoras (Dicaearchus in Porphyry, VP 19). Our information about Hippasus is sketchy, because he evidently did not write a book. Demetrius of Magnesia (1st century BCE) reports that Hippasus left nothing behind in writing (Diogenes Laertius VIII 84) and this is in accord with the tradition that Philolaus was the first Pythagorean to write a book.