Actually, I was not so much interested in the semantics of opposing forces or contradictory forces. The idea of two paired entities that form each others opposites and/or partner has been known for a long time in cultures like that of China, India and ancient Greece. But there is in general a difference in looking at those two entities - in Western thinking we see it more as good versus bad, us versus them, human versus nature, man versus woman and only one can be a winner.
Several of the eastern ways of thinking are more about cooperation, coming together, joining of these entities or forces or elements or etc.This last way of looking at it is also more conform modern Biology then the Western way of thinking. And seems to fit more with Aikido and other budo.
But the In-Yo point I made was just an aside. I was reacting on Mark Murray's post nr 26. And especially the quote of Mary Heiny with Mark Murray's response on it I found interesting.. I feel Mary Heiny is right when she comments on O Sensei's quote; "Aikido is not a fighting art". I think O Sensei's thinking goes beyond that. That is why I mentioned the importance of the mitama, musubi and misogi in understanding masakatsu a katsu katsu hayabi.
I'll leave the meat of Mark's comments on Mary to Mark, but wasn't his in-yo point exactly that - the connection of two (let's say "different") forces?
Where has he mentioned anything about one force winning?