s
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.

XXV. However, let us say no more about this. Undoubtedly, when opinion and
perception are put an end to, the retention of every kind of assent must
follow; as, if I prove that nothing can be perceived, you would then grant
that a philosopher would never assent to anything. What is there then that
can be perceived, if even the senses do not warn us of the truth? But you,
O Lucullus, defend them by a common topic; and to prevent you from being
able to do so it was, that I yesterday, when it was not otherwise
necessary, said so much against the senses. But you say that y