Sort of like why Ikeda Sensei is bringing in Ushiro Sensei from karate to teach kokyu, eh, and teach it with the Sanchin kata? It has to do with a basics that preceeds "irimi", "tenkan", and all waza.
Mike, it's interesting you mentioned this. I was talking to a Jr. High School kid today who studies karate and mentioned this stance and kata, but she had no idea what I was talking about. I was showing her the, for lack of appropriate terms, centering stance of Mr. Sum, at least my version of it. Nice cowinkidink. I found it a bit odd she wasn't familiar with the stance or kata, though. Nonetheless, perhaps the substance does exist as a substrate of other arts, and as aikidoka absorb what they will and make aikido their own, other arts have done the same with this substance.
I had class tonight and lots of theory floating around in my head. I noticed there were but a few things that I conciously tried to do. Stand with better posture, release the tension in my shoulders, maintain better connection, keep my center/weight down, breathe and move smoother and try not to force techniques. These kinds of things seem so vague and yet seem so important to me. As others have said, you need to feel it to understand it. And if these ideas are internal and lacking substance, would it not, therefore, be virtually impossible to teach? How does one teach what lacks form? It seems to me, after having felt these things through technique, that we assimilate both(if we're lucky) and at some point are able to express to others through technique(be it complex or simple, our choice)how we feel aikido is to us.
Kind of like whistling in a way. I might be able to tell you to pucker up and blow and you might then whistle. But it's still gonna take you a little longer to zero in on how to change pitch and even longer to whistle in tune.
Still, nice to ponder.