On the Enchiridion and The Education of the Prince, see the Introduction and note 123 p.105 . The reference to Plato and drinking-matches alludes to the Symposium. The line from Horace is quoted from the Satires (I, I,24-5) and the reference to Lucretius alludes to the de rerum natura, I, 935 ff.
Erasmus's defence of his Folly contains some special pleading. He is trying to win Dorp's support in the controversy which the publication of the Greek New Testament is bound to raise. In claiming that he is reasonable and sweet-tempered, that he has been misjudged and that the Folly does not go beyond the Enchiridion, Erasmus is admitting to less than the whole truth. In quoting Plato, Horace and Lucretius, he is protecting himself behind a little Folly-like banter.
Dorp's letter explained Augustine's advice (in the de doctrina Christiana) to have recourse to the Greek sources by the absence at that date of any officially received Latin text of scripture. Since Augustine's day the Greek text, too, had probably become corrupt. Dorp was worried about what Erasmus's Greek text, with its revelations of the Vulgate's inadequacies, would do to the authority of scripture and, by later calling Augustine a `dialectician', he showed that he wished to use his authority in an anti-humanist sense.
Erasmus, however, knew that Augustine also taught in the de doctrina Christiana both the necessity of consulting Hebrew and Greek texts and the necessity of grammatical correction. He therefore here unnecessarily mentions the de doctrina Christiana, as if announcing his intention of making Dorp's weapon boomerang on him. In his reply, Dorp juggles with quotations to try to turn Jerome's authority against Erasmus.
The idea that truth requires to be wrapped in fable if it is to be understood by the simple is neoplatonist. It is exploited later in the century by Dorat and Ronsard.