[[A generation is thirty years, in which time the progenitor has engendered one who generates. the cycle of life lies in this interval, when nature returns from human seed-time to seed-time.]] (Kahn, 95)
This fragments comes from Plutarch. It is not included in the Diels-Kranz German translation or those English translations, such as Robinson’s and Sweet’s, that follow it. Heraclitus, as we have seen, is interested in natural orderings and laws. What he doesn’t seem to recognize here is the largely conventional nature of this ordering. We could define a generation as 20 years (as is typical now), or 15, or perhaps 35. The main biological point of reference for our normal determination of a generation is that one’s own child becomes, him- or herself, of child-bearing age. Heraclitus’ determination here includes the period from a parent’s child bearing to the time that this individual becomes a grandparent.