Moreover, if people suppose that knowledge of anything is impossible, they do not even know whether knowledge of the impossibility of knowledge is possible, since, on their own admission, they know nothing. Against such people, who have planted themselves with their head in their own footprints, I disdain to argue. However, if I were to concede that they do have this knowledge, I would put the following questions to them. Since they have never before encountered anything true, how do they recognize knowledge and ignorance? What has given them their conception of truth and falsehood? What proof have they that the doubtful differs from the certain?
[Lucretius,
On the Nature of Things, Martin Ferguson Smith, tr., Hackett (Indianapolis: 2001) pp. 112-113.]
