Thanks for filling me in! And pardon my taking liberties or poetic license. I first encountered physis in Martin Heidegger’s An Introduction to Metaphysics (pp 13-17, the 1987 Yale University Press paperback, ISBN 0-300-01740-5) and accepted his interpretation, trusting his scholarship. (I know Heidegger can get carried away sometimes.)

Heidegger equated physis with “the essent” which Ralph Manheim translated from the book’s original German “Seiendes”) which I take roughly to mean “Being.” On pp 95-98, Heidegger goes to say the one of Parmenides and the flux of Heraclitus applied to the essent, which again, I accepted. However, I think physis is much richer and more evocative than essent, so I went with essent.