24. Although some philosophers have written on this subject,—Panætius, A Stoic philosopher who lived and taught at Athens, c. b.c. 120. His chief work was a treatise περὶ τοὺ καθήκοντος, which Cicero himself afterward used as the groundwork of his own book de Officiis. for instance, and his son amongst the Greek, Cicero amongst the Latin, writers—I did not think it foreign to my office to write also myself. And as Cicero wrote for the instruction of his son, Cic. de Off. I. 2. so I, too, write to teach you, my children. For I love you, whom I have begotten in the Gospel, no less than if you were my own true sons. For nature does not make us love more ardently than grace. We certainly ought to love those who we think will be with us for evermore than those who will be with us in this world only. These often are born unworthy of their race, so as to bring disgrace on their father; but you we chose beforehand, to love. They are loved naturally, of necessity, which is not a sufficiently suitable and constant teacher to implant a lasting love. But ye are loved on the ground of our deliberate choice, whereby a great feeling of affection is combined with the strength of our love: thus one tests what one loves and loves what one has chosen.