hen," argues our adversary, "did your Stoic philosopher
Zeno, when he had promised a loan of five hundred denarii to some
person, whom he afterwards discovered to be of doubtful character,
persist in lending it, because of his promise, though his friends
dissuaded him from doing so?" In the first place a loan is on a
different footing to a benefit. Even when we have lent money to an
undesirable person we can recall it; I can demand payment upon a certain
day, and if he becomes bankrupt, I can obtain my share of his property;
but a benefit is lost utterly and instantly. Besides, the one is the act
of a bad man, the other that of a bad father of a family. In the next
place, if the sum had been a larger one, not even Zeno would have
persisted in lending it. It was five hundred denarii; the sort of sum of
which one says, "May he spend it in sickness," and it was worth paying
so much to avoid breaking his promise. I shall go out to supper, even
though the weather be cold, because I have promised to go; but I shall
not if snow be falling. I shall leave my bed to go to a betrothal feast,
although I may be suffering from indigestion; but I shall not do so if I
am feverish. I will become bail for you, because I promised; but not if
you wish me to become bail in some transaction of uncertain issue, if
you expose me to forfeiting my money to the state. There runs through
all these cases, I argue, an implied exception; if I am able, provided
it is right for me to do so, if these things be so and so. Make the
position the same when you ask me to fulfil my promise, as it was when
I gave it, and it will be mere fickleness to disappoint you; but if
something new has taken place in the meanwhile, why should you wonder at
my intentions being changed when the conditions under which I gave the
promise are changed? Put everything back as it was, and I shall be the
same as I was. We enter into recognizances to appear, yet if we fail to
do so an action will not in all cases lie against us, for we are excused
for making default if forced to do so by a power which we cannot resist.

XL. You may take the same answer to the question as to whether we ought
in all cases to show gratitude for kindness, and whether a benefit ought
in all cases to be repaid. It is my duty to show a grateful mind, but
in some cases my own poverty, in others the prosperity of the friend
to whom I owe some return, will not permit me to give it. What, for
instance, am I, a