To obtain enlightenment in martial art means the extinction of everything which obscures the "true knowledge", the "real life". - Sijo Bruce Lee
The practice of Zen is a difficult one. It is said that any practice of Zen requires three energies; great faith, great perseverance, and great doubt. One must have faith that the practice of Zen is worth undertaking. One must have great perseverance to go through mental, physical, and spiritual austerities inherent in Zen training. All three energies are needed in equal measure, sometimes one more than the other. However, it is great doubt that could be said to be the core of Zen practice, the ability to continually introspect and ask “What is this?”
This doubt must carry itself through the entirety of one’s martial art practice. Nothing must ever be taken for granted. Any doctrine must be thoroughly questioned. Nothing can be rejected out of hand, nor can anything be accepted blindly. Within Jeet Kune Do, even those things agreed upon must be thoroughly investigated by each individual, for Jeet Kune Do can become as doctrinal as any other system of thought. The practitioner must doubt everything, from the techniques being practiced, to their own nature. This is the humility of practice. One must never consider to have arrived at the place of knowing, but continually doubt, continually examine, continually introspect, and continually learn.
In some ways, the new student to Jeet Kune Do who has never studied martial arts before has an advantage over someone with years of experience coming to the practice. They have not accumulated the many years of doctrinal thinking found in systems that approach combat in partiality. However, even within Jeet Kune Do study, they will soon create their own doctrinal patterns that will eventually need to be introspected upon. In this way, sometimes the experienced martial artist has the advantage when beginning Jeet Kune Do practice. Sometimes it is the sick man who recognizes his symptoms the best.