Seishin means: mind, soul, heart, spirit, intention, and I have to admit that the variety of these meanings are all true.
When sensei moved it look like he was doing nothing, playing only with uke’s mind. I was lucky to be uke a few times and each time I had the feeling I was totally lost. There was no danger, sensei was not violent, on the contrary, he was very relaxed as if not concerned by my useless attempts to get him.
He explained later that this Seishin no jutsu was based on the concept of kyojitsu no Kûkan 虚実 の 空間, or to put it in other words, to understand the 虚実混交, kyojitsu konkô, “a mishmash of truth and untruth, a mixture of fiction and fact”. By “making believe” that reality is not and conversely, Sensei makes his uke react in a way that is always detrimental to his survival. Interacting with Inyo, and time and space at the same time, Sôke destroys our willingness to fight.
We have to develop this ability to act without intention (seishin) and not give any strength to the opponent. When sensei was demonstrating he said that it is done without grabbing but applied with the whole body. The difficulty is to “move” the attacker without really using force.
This is when sensei added one extra level to his Seishin no jutsu by speaking of Zero no chikara ゼロ の 力 or 無 の 力, the power of Zero. The power of zero is what is experience when we take the Sakki 殺 気 test.
In fact after this class I begin to understand the simple complexity of Hatsumi sensei’s vision. The bujinkan is about releasing the “natural movement ” and this is achieved when we are always one i.e. zero at the Sakki level.