Thanks for this Lee. Between your post above and reading this post from Dan in another thread
really helps me understand what it is I will feel when I am looking for it.
If I understand correctly, someone who has the most most basic part of In Yo/Yin Yang internalized will be unmovable when pushed upon from any angle on their body while standing naturally, feet shoulder width apart, no deep stances etc.. and even be able to lift one leg at a time while the push is being applied. Generally the push is applied to their upper body.
So until such time as I can go a meet Dan, I can try to find a Taiji (or someone proclaiming internal ability) teacher and ask them to let me try and push them over. If I cannot push them.. it may be worth sticking around to learn the basics.
Would that be a fair assessment?
If they have to take a step, turn away, push back into you in any way, toss you out, or otherwise do some "waza" to deal with your push, then there's not much there for you as regards IP. If, while you are pushing on them, they can make you move, or otherwise feel like no matter what you do you can't feel where the force of your pushing on them is even going, while barely or not moving themselves, and without you feeling how you were moved (in reality some of your own force coming back into you, from many directions at once no less that you can't predict and which you shouldn't be able to feel as your own)... and being tossed explosively does not count (don't be impressed by "fajin")... then maybe they've got some as regards yin and yang for you too.