XI. Cleanthes makes use of the following example:--"I sent," says he, "two slaves to look for Plato and bring him to me from the Academy. One of them searched through the whole of the colonnade, and every other place in which he thought that he was likely to be found, and returned home alike weary and unsuccessful; the other sat down among the audience of a mountebank close by, and, while amusing himself in the society of other slaves like a careless vagabond as he was, found Plato, without seeking for him, as he happened to pass that way. We ought," says he, "to praise that slave who, as far as lay in his power, did what he was ordered, and we ought to punish the other whose laziness turned out so fortunate." It is goodwill alone which does one real service; let us then consider under what conditions it lays us under obligations. It is not enough to wish a man well, without doing him good; nor is it enough to do him good without wishing him well. Suppose that some one wished to give me a present, but did not give it; I have his good will, but I do not have his benefit, which consists of subject matter and goodwill together. I owe nothing to one who wished to lend me money but did not do so, and in like manner I shall be the friend of one who wished but was not able to bestow a benefit upon me, but I shall not be under any obligation to him. I also shall wish to bestow something upon him, even as he did upon me; but if fortune be more favorable to me than to him, and I succeed in bestowing something upon him, my doing so will be a benefit bestowed upon him, not a repayment out of gratitude for what he did for me. It will become his duty to be grateful to me; I shall have begun the interchange of benefits; the series must be counted from my act. XII. I already understand what you wish to ask; there is no need for you to say anything, your countenance speaks for you. "If any one does us good for his own sake, are we," you ask, "under an obligation to him? I often hear you complain that there are some things which men make use of themselves, but which they put down to the account of others." I will tell you, my Liberalis; but first let me distinguish between the two parts of your question, and separate what is fair from what is unfair. It makes a great difference whether any one bestows a benefit upon us for his own sake, or whether he does so partly for his own sake and partly for ours. He who looks only to his own interests, and who does us good because he cannot otherwise make a profit for himself, seems to me to be like the farmer who provides winter and summer fodder for his flocks, or like the man who feeds up the captives whom he has bought in order that they may fetch a better price in the slave market, or who crams and curry-combs fat oxen for sale; or like the keeper of a school of arms, who takes great pains in exercising and equipping his gladiators. As Cleanthes says, there is a great difference between benefits and trade.