appearance, which can deserve or obtain no credit if the mark by which we are to distinguish truth from falsehood be taken away. But that is a monstrous absurdity of yours, when you say that you follow what is probable when you are not hindered by anything from doing so. In the first place, how can you avoid being hindered, when what is false does not differ from what is true? Secondly, what judgment can be formed of what is true, when what is true is undistinguishable from what is false? From these facts there springs unavoidably ἐποχὴ, that is to say, a suspension of assent: for which Arcesilas is more consistent, if at least the opinions which some people entertain of Carneades are correct. For if nothing can be perceived, as they both agree in thinking, then all assent is taken away. For what is so childish as to talk of approving of what is not known? But even yesterday we heard that Carneades was in the habit, at times, of descending to say that a wise man would be guided by opinion, that is to say, would do wrong. To me, indeed, it is not so certain that there is anything which can be comprehended, a question which I have now spent too much time in discussing, as that a wise man is never guided by opinion, that is to say, never assents to anything which is either false or unknown. There remains this other statement of theirs, that for the sake of discovering the truth, one ought to speak against every side, and in favour of every side. I wish then to see what they have discovered. We are not in the habit, says he, of showing that. What then is the object of all this mystery? or why do you conceal your opinion as something discreditable? In order, says he, that those who hear us may be influenced by reason rather than led by authority. What if they are influenced by both? would there be any harm in that? However, they do not conceal one of their theories, namely, that there is nothing which can be conceived. Is authority no hindrance to entertaining this opinion? It seems to me to be a great one. For who would ever have embraced so openly and undisguisedly such perverse and false principles, if there had not been such great richness of ideas and power of eloquence in Arcesilas, and, in a still greater degree, in Carneades? XIX. These are nearly the arguments which Antiochus used to urge at Alexandria, and many years afterwards, with much more positiveness too, in Syria, when he was there with me, a little before he died. But, as my case is now established, I will not hesitate to warn you, as you are my dearest friend, (he was addressing me,) and one a good deal younger than myself.