James Adam, The Republic of Plato

ὅτι -- καθιστάναι: lit. ‘that we must appoint philosophers in the persons of our most perfect guardians,’ i.e. that the rulers we appoint must be philosophers. The ἀκριβέστατοι φύλακες are the same as the τέλεοι φύλακες of IV 428 D: and the whole expression is equivalent to ὅτι φιλοσόφους δεῖ εἶναι τοὺς ἀκριβεστάτους φύλακας οὓς καθίσταμεν. To read καθεστάναι for καθιστάναι (with v) is much less elegant; still less should we follow D. and V. in transposing φύλακας and φιλοσόφους. For the sense of ἀκριβεστάτους cf. (with Jackson) I 341 B, 342 D.

διεσπασμένη. Cobet proposes διεσπασμένα, which he wrongly asserts to be the reading of A. But the parts of the philosophic φύσις are not torn asunder; it is the φύσις itself which is in partes disiuncta. Bywater's διεσπαρμένα avoids this difficulty; but διεσπασμένη is much better, because it suggests that the disjunction is ‘unnatural’ (in the Platonic sense of παρὰ φύσιν): see on IV 443 B. The philosophic nature ought to be born whole.