But, for obtaining temporal favours, prayer is more effective than meritorious works, provided that the granting of the petition be not against the designs of God or the true welfare of him who prays . The just man may merit de congruo for others (e.g., parents, relatives, and friends) whatever he is able to merit for himself: the grace of conversion, final perseverance, temporal blessings, nay even the very first prevenient grace (gratia prima prœveniens), (Summa Theol., I-II, Q. cxiv, a. 6) which he can in no wise merit for himself. St. Thomas gives as reason for this the intimate bond of friendship which sanctifying grace establishes between the just man and God. These effects are immeasurably strengthened by prayer for others; as it is beyond doubt that prayer plays an important part in the present economy of salvation.