Jerome’s Tract on the Perpetual Virginity of the Blessed Virgin appeared about 383, and was written at Rome in the episcopate of Damasus (363–384).  The work of Helvidius which Jerome controverted was not published till about 380, and there can be no reference to him in the passage in the text.  Basil is contending against the general Arian inference, rather than against any individual statement  as to who the “Brethren of the Lord” were.  cf. also dub. Hom. in Sanct. Christ. Gen. p. 600. Ed. Garn.  On the whole subject see Bp. Lightfoot, in his Ep. to the Galatians, E. S. Ffoulkes in D.C.B. s.v. Helvidius, and Archdeacon Farrar in his Life of Christ, chap. vii., who warmly supports the Helvidian theory in opposition to the almost universal belief of the early Church.  Basil evidently has no more idea that the ἕως οὗ of Matt. i. 25, implies anything as to events subsequent to the τόκος than the author of 2 Sam. had when he said that Michal had no child till (LXX. ἕως) the day of her death, or St. Paul had that Christ’s reigning till (ἄχρις οὗ) He had put all enemies under His feet implied that He would not reign afterwards.  Too much importance must not be given to niceties of usage in Hellenistic Greek, but it is a well-known distinction in Attic Greek that πρίν with the infinitive is employed where the action is not asserted to take place, while it is used with the indicative of a past fact.  Had St. Matthew written πρίν συνῆλθον, the Helvidians might have laid still greater stress than they did on the argument from Matt. i. 18, which St. Jerome ridicules.  His writing πρὶν ἢ συνελθεῖν is what might have been expected if he wished simply to assert that the conception was not preceded by any cohabitation.