Aristotle mentions, as an expression of magnanimity, that one give in return more than what was originally given to you, since in that way the other person is blessed, as it were, by dealing with you, and furthermore he now becomes indebted to you--which presumably will encourage him to initiate another round of reciprocal giving (NE IV.3 1124b10-12).
Cicero in De Officiis recommends something similar, although he does so under his treatment of the virtue of liberalitas, a species (he considers) of iusitia, not under magnitudo animi:
Quodsi ea, quae utenda acceperis, maiore mensura, si modo possis, iubet reddere Hesiodus, quidnam beneficio provocati facere debemus? an imitari agros fertiles, qui multo plus efferunt quam acceperunt? Etenim si in eos, quos speramus nobis profuturos, non dubitamus officia conferre, quales in eos esse debemus, qui iam profuerunt? (I 48)Since I agree with Aristotle that the point of studying ethics is not simply to know what virtue is but also to become good (and that these may come apart), during the Mayweek Seminar I decided at one point to attempt to put this advice into practice.
For if, as Hesiod commands [Works and Days 349-51], you should return in greater measure, provided that you can, anything that you have needed to borrow, what should we do when challenged by an unsought favor? Should we not take as our model the fertile fields, which bring forth much more than they have received? We do not hesitate to perform dutiful services for those whom we hope will assist us in the future; what, then, ought we to be like towards those who have already assisted us? (Adkins)
At lunch with some graduate students I found myself short for paying my share of the tab. One student kindly lent me £2. The next day, I purposefully brought to the seminar £3 in change, and, when this student was leaving the room at the end of the session, I placed that sum in his hand. He had a chance to look at the money and count it before he went out the door, and then he turned to me and said, "It was only £2! You gave me one pound too many." "But that's the magnanimous thing to do," I said, "I'm repaying you with more than you lent me." "Don't be silly" he said (or something to that effect) and placed the pound piece on the table next to me.
So much for my attempt to be magnanimous! Reflecting on this I drew the following lessons. First, the maxim of Cicero and Aristotle cannot easily be carried out if the exchange involves money. A main purpose of money seems to be to allow exact and equal exchanges--to be able to reckon up the columns and make sure that debits equal credits. Money is therefore not a suitable medium for a 'magnanimous' exchange. Second, the benefit is best returned in such a way that the other person has no opportunity to reject the excess in favor of equality: even with a return of money, my plan might have worked if I had left £3 in an envelope for the person at the Porter's Lodge of his college. (And yet how might one indicate with suitable refinement that the extra sum wasn't a mistake?)
Another instance of sputtering magnanimity: Last winter, I was shoveling snow from the long driveway at my home, when a neighbor driving past with a plow on his pick-up truck offered to do the job for me. Especially as the snow was wet and heavy, I without hesitation welcomed the help. (He accomplished in about 30 seconds what would have cost me two hours and a sore back.) I knew that I could have paid someone $20 for the job, and that he had bought a plow for his truck whereas I hadn't, so I asked him whether I could give him some money for the service. He refused this, as I expected, but then he said, "Sam Adams is my favorite beer. I would never refuse a six-pack." Waiting a few days, so that the exchange was 'more free', but not too long, so that I wouldn't seem to be slow to show gratitude, I bought a case of beer for him instead and left it on his porch. This was all in keeping with the principle of magnanimity--the value of the beer was greater, yet since the value of each good was indefinite, and they could not strictly be compared, he might accept the gift, recognizing it was in some sense 'more', but recognizing also that we were counting it as an 'even' and a friendly exchange.
But even this effort at magnanimity, I later thought, was flawed. It would have been better had I waited until he was home to drop off the beer. My simply leaving the beer at his house made the exchange too much like a commercial exchange of services and insufficiently friendly--an exchange of things, rather than affection or time. Much better would have been additionally to sit down with him, share one of the beers, and talk. (As it is, he lives a quarter mile down our country road, and I hardly see him. This was a missed chance to start a friendship.)