Lucretius, De Rerum Natura 4.469-477
“In addition, if anyone thinks nothing can be known, he does not know
whether or not it can be once he confesses that he knows nothing.
Therefore, I decline to argue a case against a man
who has assigned his head to his own footsteps.
Nevertheless, should I concede that he knows at least that,
I would still ask him this: since he saw nothing true in the material world before
how could he know what there is to know or to not know in turn
or what provided him with a difference between true and false
and what matter distinguished the uncertain from the sure?”
Denique nil sciri siquis putat, id quoque nescit
an sciri possit, quoniam nil scire fatetur.
hunc igitur contra minuam contendere causam,
qui capite ipse suo in statuit vestigia sese.
et tamen hoc quoque uti concedam scire, at id ipsum
quaeram, cum in rebus veri nil viderit ante,
unde sciat quid sit scire et nescire vicissim,
notitiam veri quae res falsique crearit
et dubium certo quae res differre probarit.