Why do you think the Samurai studied Zen? I really don't know, but I do know this. To study Zen is the very study of how we as human beings can live in peace and harmony. And to me, this is the highest form of Goshin, or Self-Defense. The practice of Zen is not a means of escape from reality, but as the Samurai knew, a direct encounter with your life as it is.
For instance, let's say you take a side kick to your ribs and pain penetrates your skin, muscles, all the way to bone and marrow. Perhaps you might say a few choice words, but in reality there is nothing really to say. All you can do is hold your ribs. Trying to understand the pain intellectually or philosophically is not going to help. All there is is you holding your ribs tasting the pain deeply.
In this moment is your opportunity for seeing and understanding your life as it is. You are here...you are now. Just like having your ribs kicked in, Zen practice and your daily life are the same. It is urgent. It is now. It is simultaneously the means and the end. This is where peace and harmony occur. To practice Zen is to 'see' this. Zen practice is simply eating breakfast, getting ready for work, practicing kata, taking a piss and being polite and mindful with friends and family.
It is from this practice that we see life from a new perspective. Life simply is as it is. Empty and open. Zen practice accomplishes this by uniting us with the Universal part of ourselves which is anchored in peace and harmony. When we live in peace and harmony all sense of Self vanishes as a dream fades when we awaken. The need for Self-defense ceases to exist as the fear of death and dying have faded with the Self. This is why I consider Zen the best form of Self-Defense. Perhaps this is one reason why the Samurai practiced Zen?
DO WHAT YOU CANNOT DO
1 day ago