Attached to this message is an article by David Sedley that contains a lot of interesting information about Epicurus' views on "dialectic" (presumably referring to "logic" - or as Sedley says "syllogistic, deﬁnition, division, partition, the resolution of sophisms and logical principles governing the assignment of truth and falsity").
Sedley is one of my favorite living writers on Epicurus. I am posting this without studying the article in full but I feel sure that the analysis here will be helpful to our topic in this forum on the Epicurean Canon of Truth. The views of Epicurus on the use of some aspects of logic are complex (or at least seem to appear that way to us today) and this is an important topic for understanding Epicurus' view of truth.
Sedley develops this discussion through reference to "the Bat Riddle":
The Bat Riddle
At the end of Republic book 5, Plato’s Socrates argues that scientiﬁc knowledge (epistêmê) focuses on Forms, while sensible particulars are the domain of unstable ‘opinion’ (doxa). For example, while Beauty (the Form) corresponds to pure ‘being’ and can therefore be known, ‘the many beautiful things’ no more are beautiful than they are not beautiful and therefore cannot be known. Down to this point, the antithesis has been argued only with regard to pairs of opposite predicates – beautiful/ugly, large/small, double/half and so on. But in the closing remarks of the discussion Glaucon hints at its broadening so as to cover substances too:
‘It’s like the double meanings at feasts’, he said, ‘and the children’s puzzle about the eunuch, his shooting the bat – their puzzle about what he did it with and what the bat was on. For these too [i.e., the cases of opposites] are ambiguities, and it is impossible to think reliably of each of them as either being or not being, or as both, or as neither.’
More quotes of interest:
In that last footnote 44 Sedley is referring to this following passage from Lucretius, here translated by Martin Ferguson Smith:
This article by Sedley contains extensive discussion of Epicurus' view of the Platonic / Aristotelian "Bat riddle" about the implications of referring to bats as birds. It seems to me that all of this is a good example of how Epicurus was deeply concerned about refuting word games, and this would then constitute a prime example for the argument that the "limit of pleasure" / painlessness terminology was intended as a specific logical rejoinder to the anti-Pleasure argument in Plato's Philebus (just as Epicurus was responding to this argument in Plato's Republic, per Sedley), and not (as it is used by Stoics/Neo-Epicureans today) as a full and complete definition of the goal of human life.
And always remembering that the Randians' favorite, Aristotle, was essentially in the same camp as Plato, here we see that Epicurus objected to both:
And this shows that Platonic-Aristotelian connection, which would suggest that the Epicurean line about walking around endlessly prating about the meaning of "the good" was aimed as much or more at Plato than at Aristotle:
There is important information in this article too about Epicurus' arguments against determinism: