Taekwondo Bible, Vol. 2
This book, On Samjae and Kang-Yu of Taekwondo, was written in 2003 in Korean and published in 2003 in Korea(ISBN 89-7889-060-1). This book is under translation. Of course, you can see the whole test on this site as translated by me, but it is not perfect: It needs much polishment.
Samjae means the three essential materials(Haneul(Heaven), Tang(Earth) and Saram(Man)) and Kang-Yu the hardness and the softness. The Samjae and Kang-Yu are the main concepts of Taekwondo and its philosophy but they are neither only familiar to western people nor explicit to Koreans. Especially although those concepts have been regarded as very important ones in oriental philosophy general they have never been investigated logically and in the relations with Taekwondo.
This article aims to explain them explicitly in logical aspects of them and why they should be main concepts of Taekwondo philosophy. Following those investigation you will see they are the very essential framework not only of every Taekwondo skill but also of all kinds of martial skills, and they are also the structure building your spirit. This task will lead you to understand the whole relations among training, skill, spirit and life explicitly. Thus, I wish, you will find the ultimate framework of all kinds of martial arts though in abstract level in this discussion.
The entire discussion relies on "The Philosophical Principles of Taekwondo" at first, so I recommand you try all the texts of PPT.