Another long-winded (but non-obsessive! ) "talking to myself out loud” as I sort through some of the posts here:
there is in fact no absolute standard of right and wrong as to how to define words
Which is something even the dictionarists grapple with; and their standard really is evolving conventional usage. Reminds me of a quote by Wittgenstein (in On Certainty, I think): “Don’t look for the meaning, look for the use.”
And whatever other standards there are, are contextual – as you point out; e.g. the word “utility” has a different meaning in economics (borrowed from the philosophical utilitarians) than in everyday discourse.
Folks like Aristotle and Plato (and others) seem to want to make a map that is a standard to judge the territory – whereas any map must be judged by the territory, not the other way round. Epicurus’ mapping (because if you’re a teacher or a therapist, you need to map) seems more designed to point to the territory (reality in all its existential and experiential variability) – a bit like the Zen parable about fingers pointing to the moon. And that certainly does not require the kind of “religious” faith that, say, Plato does. Whatever faith there is a testable faith, meant to be tested in everyday life in all its everydayness.
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You mentioned “obsessing” earlier. I think that Epicurus wanted to free us from all obsessiveness – which is just another form of tarache. Even the task of unpacking and interpreting Epicurus’ maps is measured, in its goodness, by pleasure and enjoyment, as per VS27: “In the case of other occupations the fruit (of one's labors) comes upon completion of a task while (in the case) of philosophy pleasure is concurrent with knowledge because enjoyment does not come after learning but at the same time (with) learning.”
[One of the reasons I liked Frances Wrights book so much was that her portrait of Epicurus as anything but obsessive; in fact sometimes disarming others’ obsessiveness with humor, and always in an easygoing manner – but without surrender.]