Today this question is on my mind, regarding the often used negation in Epicurean philosophy (which came up when thinking about the phrase; "absence of pain") ...and of which there are many many concepts presented as a negation.
And I did this search online:
How do we cognate concepts framed in the negative, and can we rephrase concepts in the positive and still keep a correct representation. 
Here is a further article:
Thinking aloud here.
"This is not pleasurable" gives me a notably different impression than "this is painful". "This is not pleasurable" brings to my mind some sort of neutral middleground, which as we know does not exist under the Epicurean framework. Perhaps this explains why people get so hung up on "absence of pain" implying some sort of ascetic nirvana-esque state. Not because of unclearness on Epicurus' part, but because they don't know or don't understand the idea that there is only pleasure and pain, and the way the brain processes negation points them to this non-existent "neutral third state".
Interesting thread!
