You raise some solid points, Little Rocker . I especially find intriguing that statement: a "a 'proleptic' capacity or capacities that produce prolepseis". So, if I understand correctly, you're positing a mental capacity/faculty/process/function that leads to or produces something we can call a "prolepsis." And, since the texts use the plural, there has to be some significance to including it with sensations and feelings (pleasure and pain). For example:
Now in The Canon, Epicurus affirms that our sensations (plural: τὰς αἰσθήσεις) and preconceptions (plural: προλήψεις) and our feelings (plural: τὰ πάθη) are the standards of truth ; the Epicureans generally make perceptions of mental presentations (τὰς φανταστικὰς ἐπιβολὰς τῆς διανοίας) to be also standards.
The interesting thing (per LSJ) about "sensations" αἰσθήσεις is that it can not only refer to "physical sensations through what we think of as the sense-organs (eyes, ears, nose, etc.) but "also of the mind, perception, knowledge of a thing." The citations are to Plutarch, so maybe that's a later connotation? Although LSJ also references Plato in Philebus (emphasis added):
Socrates: When a man receives from sight or some other sense (αἰσθήσεως) the opinions (δοξαζόμενα doxazomena) and utterances of the moment and afterwards beholds in his own mind the images of those opinions and utterances.
So, the sensations of "the opinions and utterances" received "from sight or some other sense" give rise (according to Plato) to sustainable mental images that we can hold, discuss, etc. in our minds. The prolepsis, as defined by LSJ, are "mental picture or scheme into which experience is fitted." So, the sensations come pouring in, and, are then fit into "mental pictures or schemes" to make sense of them. I'm getting the image of one of those old-time coin sorters that you could put coins into, they'd roll down a little ramp, and then fall into the correct sized slot: pennies (smallest) first, then dimes, etc. The "proleptic" faculty would be like the sorting machine... and the prolepseis would be the tubes into which the coins fell, depending on their size.
But that doesn't move us along from Epicurus's "content" of the prolepsis of the gods being "blessed and uncorrupted", does it?
Long & Sedley in The Hellenistic Philosophers (login with free account to view the link) cite the Letter to Herodotus as showing that prolepseis are necessary to get at the underlying meaning of words. The citation doesn't use the word prolepsis but I can see where they get that it's being discussed:
"In the first place, Herodotus, you must understand what it is that words denote, in order that by reference to this we may be in a position to test opinions, inquiries, or problems, so that our proofs may not run on untested ad infinitum, nor the terms we use be empty of meaning. [38] For the primary signification of every term employed must be clearly seen, and ought to need no proving58; this being necessary, if we are to have something to which the point at issue or the problem or the opinion before us can be referred.
It seems to me that the faculty of the prolepsis is what it is that provides us the ability to "understand what it is that words denote," and ,by reference to this, we can test opinions, etc. I also like that Epicurus literally says that the "primary signification" of every term but be "clearly seen" (φθόγγον βλέπεσθαι)... like that coin dropping into its proper slot.
So, what's the point of these early morning musings? The prolepsis (to me, as of 7:21 am on a Tuesday 
) seems to imply both a mechanism of the mind as well as a reference to making sense of sense perceptions. It involves both the sorting of sensations as well as the slots into which the sensations fits in their respective patterns.
