Robert M Watson Jr
I really regret not being able to read the characters of either Chinese nor Japanese as 'shin' has always confused me. In Japanese 'shin' actually refers to three or four (at least) different characters and concepts heavenly(or divine), mind/heart/spirit (kokoro), true, body (mi-which also means fruit/nut) and new. Something like shin shin toitsu uses two different characters and means spirit body toitsu so I'm still a bit confused.
Here 'Xin' must mean mind/spirit/heart? I don't quite understand the difference between 'desire' and 'intent' in this context.
Well, the basic implication in much of the discussion about "internal" arts is that the mind causes forces to exist. That's what they mean by "intent" and all sorts of other phrases along those lines. When Ueshiba, Tohei, and a myriad of other Asians demonstrate that they can stand at impossible-seeming angles, or hit incredibly hard, or not be moved by extraneous forces, they are demonstrating that instead of using normal strength to do these feats, they are using forces within their body that they have learned to do by "intent".
In the classical Asian view there was a way of looking at things that said your "desire" (which resides in the heart) then causes the mind to do something. Hence the part of the saying about "the heart (xin) leads the mind (shen)". We westerners tend to think of "desire" and "mind" being the same thing.
The idea of the mind-intent coordination (body-mind coordination) is found all over the place. The idea is found in "Xing yi" fist/boxing, in "Yi Li" (Mind Strength) boxing, in "Yi Quan" (Mind boxing), and in many other places. They all use the idea of forces manipulated by the mind (and also more than that, but I'm trying to do a thumbnail sketch).
But anyway, the short answer is that they tended to view the desire to so something as separate from the mind, hence the strange-seeming dichotomy, while we tend to think of "desire" and "mind" as facets of the same thing.