It is the result of the life-long martial arts development process Lee went through. Bruce Lee stated that his concept is not an "adding to" of more and more things on top of each other to form a system, but rather, a winnowing out.
The metaphor Lee borrowed from Chan Buddhism was of constantly filling a cup with water, and then emptying it, used for describing Lee's philosophy of "casting off what is useless".
He also used the sculptor's mentality of beginning with a lump of clay and hacking away at the "unessentials"; the end result was what he considered to be the bare combat essentials, or JKD.
The core concepts of JKD are derived from Wing Chun. This includes such ideas as centerline control, punching with a vertical fist, trapping, and forward pressure.
Through his personal research and readings, Lee also incorporated ideas from Boxing and Fencing. Later during the development of Jeet Kune Do, he would expand to include the art for personal development, not just to become a better fighter.
To illustrate Lee's views, in a 1971 Black Belt Magazine article, Lee said "Let it be understood once and for all that I have NOT invented a new style, composite or modification.
I have in no way set Jeet Kune Do within a distinct form governed by laws that distinguish it from 'this' style or 'that' method.
On the contrary, I hope to free my comrades from bondage to styles, patterns and doctrines."
One of the theories of JKD is that a fighter should do whatever is necessary to defend himself, regardless of where the techniques come from.
One of Lee's goals in Jeet Kune Do was to break down what he claimed were limiting factors in traditional martial arts training, and seek a fighting thesis which he believed could only be found within the reality of a fight.
Jeet Kune Do is currently seen as the genesis of the modern state of hybrid martial arts.
