ἄν: keeps in view the fact that the prot. ὅστις μὴ γένοιτο has just been reached as an apod. The first statement is ἡμεῖς, κακῶς πράξαντες, οὐκ ἂν ἰατροὶ γενοίμεθα. Then, starting again with this result, and selecting a single case, we have ὅστις (equiv. to εἴ τις) μὴ ἰατρὸς ἂν γένοιτο κτἑ. See GMT. 63, 2.
αὕτη γὰρ κτἑ.: the causes of the deterioration which are here mentioned are all of such a sort that loss of knowledge is occasioned by them. See on 344 e, l. 23.