"To know one, is to know ten thousand". Those are the words of Miyamoto Musashi ( 1584-1645), one of the greatest warriors in history. He took part in more than 60 duels (of which he won all) and 6 battles. He was a man whose martial arts extended far beyond the sword; a man whose philosophy for living still applies today.
After defeating perhaps his greatest opponent, Sasaki Kojiro, in one of the most famous duels ever at Ganryu Island, Musashi started to reflect more and more about life and the Way that he was pursuing through his swordsmanship. In his final years of living he retired to a small cave known as Reigan Cave, where he wrote down his thoughts and conclusions.
The Book of Five Rings is separated into (you guessed it!) five parts, representing Earth, Water, Fire, Wind and lastly Emptiness. Each of these deals with different aspects of his Niten Ichiryu ("Two Heavens-as One School") way of fencing.
In the Earth Book, Musashi discusses the basics and also includes a summary of each of the following books. In it he insightfully compares the way of Heiho (the way of becoming enlightened, loose explaination) to the way of the carpenter, discusses the name of his school (unlike was common at the time among swordsmen, Musashi fought with both his long and short sword at the same time, essentially saying that it would be foolish to die while having one of your weapons still sheathed) and rythm in life and Budo (can be compared to what Bruce Lee called "broken rythm" in his teachings of Jeet Kune Do.
In the Water Book, Musashi discusses the techniques and way of thinking in his style. "Do not become tense and do not let yourself go." Observing without using the eyes, but using something that could be called a sixth sense. Being like water. These are things of great interest, that - as Musashi so often writes, should be studied carefully.
In the Fire Book, Musashi discusses strategy of all kinds, and in the Wind book he talks about other schools and ways of martial arts (of his time), and points out their flaws and compares them to his own.
In the last book, The Book of Emptiness (or Void) - which is also the shortest of them all, barely a page long - goes in-depth with few words into what could be called the very essence of everything. Zen.
The Book of Five Rings is a timeless classic that belongs in the library of every thinker and martial artist alike. Its content has value in all areas of life, whether it be business or social matters.