This last book within Go Rin No Sho is the shortest, and perhaps the most difficult to understand. It talks of void or emptiness. However, this emptiness is not that of a vacuum or an absence. It is a space of possibility. Not where there is nothing, but where many things could be.
Musashi writes that the ignorant are sure of themselves, convinced that "their" way is the "true" way. One who understands his Heiho continually hones their skills, is always seeking to learn more, having no illusions.
The study of a true Martial Art (as opposed to a martial sport), is a never ending quest for self improvement in spiritual as well as physical terms.
The goal is the way itself.