We have said enough about authors: although you had asked me whether I did not think that since the time of those ancient philosophers, in so many ages, the truth might have been discovered, when so many men of genius and diligence were looking for it? What was discovered we will consider presently, and you yourself shall be the judge. But it is easily seen that Arcesilas did not contend with Zeno for the sake of disparaging him; but that he wished to discover the truth. No one, I say, of preceding philosophers had said positively, no one had even hinted that it was possible for man never to form opinions: and that for a wise man it was not only possible, but indispensable. The opinion of Arcesilas appeared not only true, but honourable and worthy of a wise man. Perhaps he asked of Zeno what would happen if a wise man could not possibly perceive anything, and if to form mere opinion was unworthy of a wise man? He answered, I suppose, that the wise man never would form mere opinion, since there were things which admitted of being perceived. What then were they? Perceptions, I suppose. What sort of perceptions then? In reply to this he gave a definition, That it was such as is impressed and stamped upon and figured in us, according to and conformably to something which exists. Afterwards the question was asked, whether, if such a perception was true, it was of the same character as one that was false? Here Zeno saw clearly enough that there was no perception that could be perceived at all, if the perception derived from that which is, could possibly resemble that which is derived from that which is not. Arcesilas was quite right in admitting this. An addition was made to the definition; namely, That nothing false could be perceived; nor anything true either, if it was of such a character as that which was false. But he applied himself diligently to these discussions, in order to prove that no perception originated in what was true of such a kind that there might not be a similar one originating in what was false. And this is the one subject of controversy which has lasted to this day. For the other doctrine, that the wise man would never assent to anything, had nothing to do with this question. For it was quite possible for a man to perceive nothing, and nevertheless to be guided at times by opinion; which is said to have been admitted by Carneades. I, indeed, trusting rather to Clitomachus than to Philo or Metrodorus, believe that he argued this point rather than that he admitted it.