However oblivious the pre-Socratics may have been to the ontological difference [ontologische Differenz  ] as Heidegger himself thematizes it, they had a profound sense of the Being-process, for they conceived Being [Sein  ] as φύσις   [physis]. Whatever it is that spontaneously emerges, or opens-up and unfolds, and, having unfolded, appears in abiding self-manifestation – this is φύσις. It is not   simply what we call “nature,” [Nature] which is a being like the rest, sc. only one form of emergence [Aufgehen  ]. Rather it embraces all manner and types of beings: heaven [Himmel  ] and earth [Erde  ], gods [Götter  ] and men [Mensch  ]. By reason of φύσις, beings [Seiende  ] arise and stand   forth as being what they are, sc. they become constant and observable, able-to-be-encountered. Φύσις is emergent-abiding-Power. Whence does it emerge? From concealment [Verborgenheit  ]. Recent philological research finds a relation between the stem φυ- and the φα- of φαίνεσθαι, suggesting that φύσις is an emerging-into-light, a shining-forth, an appearing [Erscheinung  ]. Hence, by reason of φύσις, ἀ-λήθεια [a-letheia] comes-to-pass [GA40  :11-12 (auigehenden und verweilenden Waltens), 54, 77 (φυ-, φάινεσθαι), 47 (ἀ-λήθεια)]. [RHPT:17]