13. Let this, then, be enacted as the first law of friendship, that we demand of friends only what is right, and that we do for the sake of friends only what is right. [Footnote: This is a virtual repetition of the law of friendship announced at the beginning of the previous section, and Cicero probably so intended it. He states the rule, then demonstrates its validity, then repeats it in an almost identical form, implying what the mathematician expresses when he puts at the end of a demonstration _Quod èrat demonstrandum._] This understood, let us not wait to be asked. Let there be constant assiduity and no loitering in a friend's service. Let us also dare to give advice freely; for in friendship the authority of friends who give good counsel may be of the greatest value. Let admonition be administered, too, not only in plain terms, but even with severity, if need be, and let heed be given to such admonition. On this subject some things that appear to me strange have, as I am told, been maintained by certain Greeks who are accounted as philosophers, and are so skilled in sophistry that there is nothing which they cannot seem to prove. Some of them hold that very intimate friendships are to be avoided; that there is no need that one feel solicitude for others; that it is enough and more than enough to take care of your own concerns, and annoying to be involved to any considerable extent in affairs not belonging to you; that the best way is to have the reins of friendship as loose as possible, so that you can tighten them or let them go at pleasure; for, according to them, ease is the chief essential to happy living, and this the mind cannot enjoy, if it bears, as it were, the pains of travail in behalf of a larger or smaller circle of friends. [Footnote: This passage seems to be a paraphrase of a passage in the _Hippolytus_ of Euripides, in which the Nurse says: "It behooves mortals to form moderate friendships with one another, and not to the very marrow of the soul, and the affections of the mind should be held loosely, so that we may slacken or tighten them. That one soul should be in travail for two is a heavy burden." Euripides was regarded, and rightly, as no less a philosopher than a tragedian, and was not infrequently styled [Greek: sophos]. Cicero here veils his thorough conversance with Greek literature and philosophy, and assumes the part of Laelius, in whose time, though Greek was not omitted in the education of cultivated men, the study was comparatively new, and was not carried to any great extent.]