Academic Scepticism 271
argument: 'if you say you are lying and you speak the truth, then you
are lying; but you do say that you are lying and you speak the truth;
therefore, you are lying'. How can you avoid approving of this argument
when you have approved of the previous one which has the same form?
These problems were put by Chrysippus, but even he did not solve them.
For what would he make of this argument: 'if it is light, it is light; but
it is light; therefore, it is light.' Surely he would allow it; for the very nature
of the conditional is such that when you have granted the antecedent you
are compelled to grant the consequent. How then does this argument
differ from the following? 'If you are lying, you are lying; but you are
lying; therefore, you are lying'. You say that you can neither approve of
this nor disapprove of it; so how can you do any better with the other?
If craft, reason, method, if rational inference itself have any force, then
they are all found equally in both arguments.- Their final position is this: they demand that these [arguments]
be excepted as inexplicable. I think they had better appeal to a tribune
for their exception; they will certainly never get it from me. Further,
they cannot get Epicurus, who disdains and scoffs at dialectic as a whole,
to grant that statements of this form are true, 'either Hermarchus will
be alive tomorrow or he will not', despite the declaration of the dialectici-
ans that every utterance with this form, 'p or not-p' is not just true but
necessary; but notice the cleverness of the man whom those dialecticians
think is slow-witted: 'if I grant that one of the two is necessary, then it
will be necessary tomorrow for Hermarchus either to live or not to live;
but there is no such necessity in the nature of things.'
So let your dialecticians, i.e., Antiochus and the Stoics, quarrel with
Epicurus; for he undermines all of dialectic, since if a disjunction of
contradictories (by contradictories I mean two statements, one of which
says p and the other not-p)-if such a disjunction can be false then none
is true. 98. So what is their quarrel with me, who follow their own
teaching on the matter? When this sort of problem arose, Carneades used
to tease them as follows: 'if my argument is sound, then I will stick to
it; but if it is unsound, then Diogenes should give me my mina back.'
For he had studied dialectic with this Stoic, and that was the fee which
dialecticians used to charge. So I follow the methods which I learned
from Antiochus; and therein I do not find any reason to judge that 'if it
is light, it is light' is true (for the reason that I learned that every doubled
conditional is true) and not to judge that 'if you are lying, you are
lying' is a conditional of the same form. Either, then, I will make both
judgements, or if I should not make the one, then I should not make the
other either.