Note 342 — LXXII (A III, 15)

Though Cicero uses tantum ... quantum here, he does not mean that Atticus failed to love him enough—that would have been too unreasonable. In a certain way he means that he loved him too much. He allowed his spontaneous feelings full vent, without acting with the cool wisdom which he would have shewn in fulfilling a duty or moral obligation. It is more fully expressed above. Still, it was a difficult thing to say, and he doesn't succeed in making it very clear.