Extra, I WAS talking about dualism (the conceptual opposition of pleasure and pain) and nondualism (the absolute uncompared and unconceptualization experience of what we call 'pain" and "pleasure").
Their relationship can be seen in the way masochists conceptualize pain as pleasure. Sadist do the same, but their situation is weaker. For example (I repeat from another thread):
The masochist drops to the floor and beseeches the sadist to hurt him.
After some thought the sadist says "No."
After some writhing with frustration the satisfied masochist answers, "Thanks."
The logic of the relationship entails the advantage of the masochist.