learners of philosophy; for here the value of the commodity cannot be measured by money, and, in fact, an exactly equivalent price cannot be set upon it, but perhaps it is sufficient to do what one can, as in the case of the gods or one's parents.
But where the original giving is not upon these terms but avowedly for some return, the most proper course is perhaps for the requital to be such as both shall allow to be proportionate, and, where this cannot be, then for the receiver to fix the value would seem to be not only necessary but also fair: because when the first giver gets that which is equivalent to the advantage received by the other, or to what he would have given to secure the pleasure he has had, then he has the value from him: for not only is this seen to be the course adopted in matters of buying and selling but also in some places the law does not allow of actions upon voluntary dealings; on the principle that when one man has trusted another he must be content to have the obligation discharged in the same spirit as he originally contracted it: that is to say, it is thought fairer for the trusted, than for the trusting, party, to fix the value. For, in general, those who have and those who wish to get things do not set the same value on them: what is their own, and what they give in each case, appears to them worth a great deal: but yet the return is made according to the estimate of those who have received first, it should perhaps be added that the receiver should estimate what he has received, not by the value he sets upon it now that he has it, but by that which he set upon it before he obtained it.
II
Questions also arise upon such points as the following: Whether one's father has an unlimited claim on one's services and obedience, or whether the sick man is to obey his physician? or, in an election of a general, the warlike qualities of the candidates should be alone regarded?
In like manner whether one should do a service rather to one's friend or to a good man? whether one should rather
