There is hence a manifold of sciences which relate to beings that are "addressed in part," and that means here "addressed by way of cutting off a piece." There are sciences which cut out, from the whole of beings, determined regions and then address those regions purely as delimited in themselves, elaborating them in λέγειν. Every such science has, as we say, its determined region. To the regions of these sciences there corresponds a definite αἴσθησις, an original perception in which the fundamental character of the objects in the region is grasped, either explicitly or not. In geometry, the objects are the relations of space or site, which are not at all given with Being as such; the objects of φυσική are beings insofar as they are in motion. The physicist does not first prove that the beings he makes thematic are in motion; they are seen that way in advance. Every strain, every autonomous region of beings, has a definite αἴσθησις which mediates the access to the primary character of its objects: space, motion, etc. That means that this μία αἴσθησις as regards what is seen is ἐν μέρει, "by way of cutting off a piece," compared to the ὅλον, "the whole." But the science that considers the Being of beings οὐδεμιᾷ ἡ αὐτή "does not coincide with any of those" that address beings by way of cutting off a piece. This becomes still clearer in the sentence that follows: οὐδεμία γὰρ τῶν ἄλλων ἐπισκοπεῖ καθόλου περὶ τοῦ ὄντος ᾗ ὄν, ἀλλὰ μέρος αὐτοῦ τι ἀποτεμόμεναι [25] περὶ τούτου θεωροῦσι τὸ συμβεβηκός (chapter 1, 1003a23f.). "None of the other sciences consider beings as a whole in their Being, but instead every one cuts out a part of them and aims its consideration at this part," or, more precisely, "at that which is proper to the beings as such which are cut off in this way." Thus, e.g., geometry considers the relations of site themselves.
ἐπεὶ δὲ τὰς ἀρχὰς καὶ τὰς ἀκροτάτας αἰτίας ζητοῦμεν, δῆλον ὡς φύσεώς τινος αὐτὰς ἀναγκαῖον εἶναι καθ᾽ αὑτήν (a26ff.). "Since we are now seeking τὰς ἀρχὰς, the starting points, that out of which the Being of beings is what it is," and precisely τὰς ἀκροτάτας αἰτίας, "the highest αἰτία, the first ones, then it is clear that these determinations, the ἀρχαί, are determinations ὡς φύσεώς τινος, of something which is present by means of itself." This last expression is telling, and it elucidates the whole idea of this science of Being in Aristotle. He can indeed say no more than Plato already said, namely that the Being of beings is itself a being; but the Being of beings is precisely something of a quite peculiar sort and cannot be characterized in turn by that which it itself categorially determines. I cannot grasp the Being of beings in turn as a being; I can grasp it only by acquiring immanent determinations for Being itself out of itself. Aristotle therefore saves himself when he says: Being and the manifold of the characters which pertain to Being καθ᾽ αὐτό are ὡς φύσεώς τινος, like something ὡς φύσις τις, "something already present by means of itself." He says φύσις in order to emphasize that these characters of the Being of beings do not pertain to beings merely insofar as they are addressed, but are already there for ἀποφαίνεσθαι, for the showing in λέγειν.