direct and guide all their other kinds of behavior. It is in and through speaking that the modes and the objects of human action are disclosed, explained, and determined. Human behavior and human being first become conspicuous in and through speaking, and so in their early, pre-scientific characterization of human being, the Greeks defined human being as ζῷον λόγον ἔχον—the living being that can speak and that co-defines its being in and through such speaking.
It is clear, then, that speaking is not something incidental but an entirely distinctive and universal state of affairs, a form of behavior whereby humans give direction to their being and bring their world into discussion. Talking, therefore, is human being’s distinctive, universal, and fundamental way of comporting itself toward the world and toward itself.
Λόγoς, then, is what reveals an ontological connection between the other two universal regions we mentioned: human being (ἦθος) and world (φύσις). So the regions that these three words designate provide us with an essential (if rough) classification of beings. Correspondingly the three disciplines of physics, ethics, and logic do not come together by chance. Rather, this threefold division and articulation is essential, and by means of it the three disciplines deal with the entirety of all beings. The basic topic of philosophy is the whole of beings; and these three disciples present us with a division of philosophical labor that we must hold to as entirely natural.
In the development of the sciences, such divisions usually come later, after the original and basic investigations have first been carried out in each of the areas. The same goes for the names of these disciplines. Usually the names get set only when the divisions get established. [4]
According to Sextus Empiricus,3, 4 Xenocrates was supposedly the first to make this division explicit. It had been already current among the Stoics, whence it passed over into Hellenistic school philosophy.
ἐντελέστερον δὲ . . . οἱ εἰπόντες τῆς φιλοσοφίας τὸ μέν τι εἶναι φυσικόν, τὸ δὲ ἠθικόν, τὸ δὲ λογικόν· ὥν δυνάμει μὲν Πλάτων ἐστὶν ἀρχηγός, περὶ πολλῶν μὲν φυσικῶν, περὶ πολλῶν δὲ ἠθικῶν, οὐκ ὀλίγων δὲ λογικῶν διαλεχθείς· ῾ρητότατα δὲ οἱ περὶ τὸν Ξενοκράτην καὶ οἱ ἀπὸ τοῦ Περιπάτου,
3. Sextus Empiricus, Πρὸς μαθηματικούς (Against the Mathematicians). The work deals with later skepticism, ca. 200 ce. Still valuable on skepticism is Paul Natorp, Forschungen zur Geschichte des Erkenntnisproblems im Altertum. Protagoras, Demokrit, Epikur, und die Skepsis (Berlin: W. Hertz, 1884).
4. [Of the eight books of Sextus Empiricus’ Πρὸς μαθηματικούς, the last two, books 7 and 8, are sometimes treated as books 1 and 2 of Sextus’ Πρὸς λογικούς (Against the Logicians). This is the case in R. G. Bury’s bilingual edition, Sextus Empiricus. The translation above, as elsewhere in this volume, follows Heidegger’s German translation of the Greek.]