For those who haven't read Teri Tom's book, "The Straight Lead: The Core of Bruce Lee's Jun Fan Jeet Kune Do", I would strongly recommend it. She is a board member of the Bruce Lee Foundation and long time student of, and certified instructor under, Ted Wong (the man who spent more personal time with Bruce than any of the other original students).
First a quote from Bruce on JKD: "Only one of 10,000 can handle it. It is complete martial art. Complete offensive attacks. It is silly to think almost anyone can learn it."
Ted Wong asked Bruce what he meant in that quote. Bruce said that most people lack the discipline to learn the simple techniques found in JKD, and keep practicing those techniques over and over and over again, knowing that you will never achieve true perfection. Bruce said the average martial arts student is more confident in learning stances, punches, and set patterns of attack and defense. But when it comes time to use this in a real fight, they are defeated by their own "classical mess".
Here are some things from the book that reveal the truth of JKD. After reading, you will understand that most of the schools claiming to teach JKD today are completely bogus. In fact, in reading the first statement you can see that one of the most famous JKD "instructors" has bastardized Bruce's system.
"JKD is NOT kali, escrima, or "27" arts"
For over 30 years, certain so-called JKD instructors have been teaching techniques that were never developed or practiced by Bruce Lee. In some cases, they have taken certain arts like kali and escrima, and misrepresented them as JKD. Nowhere in Bruce Lee's writings will you find notes on kali or escrima techniques. In fact, nowhere in Bruce Lee's private notes will you find an in-depth analysis of any arts other than Western fencing and boxing, and in earlier years, Wing Chun. If he briefly mentioned other arts, it was to understand their strengths and shortcomings, so that he could find ways to defeat them. There is no such thing as "JKD blend", as some instructors have claimed.
"JKD is not Wing Chun"
JKD is NOT a modified version of Wing Chun, as some have misrepresented it. Yes, Bruce initially studied Wing Chun. But remember, this was early in his development as a fighter. Anyone who's seen backyard training footage of Bruce knows that, by the late 60's, he'd traded his Wing Chun dummy for the heavy bag.
As noted in a letter to William Cheung (note: she is referring to a letter mentioned in an earlier part of the book), Bruce had stopped practicing Wing Chun by 1967. Some Wing Chun instructors like to claim that Wing Chun is the foundation of Jeet Kune Do and that Bruce merely expanded upon it. WRONG! He had all but abandoned it. Its shortcomings are what forced him to look for a completely different way of fighting. All of this is clearly documented in Bruce's letter to Cheung. JKD is different from Wing Chun structurally, mechanically, the footwork, etc.
"JKD is not boxing"
While Bruce may have discarded Wing Chun for the western arts of fencing and boxing, JKD is not a simplified version of those arts either. To the untrained eye, it may appear as though Jeet Kune Do is nothing more than a fancy name for boxing or kickboxing. This is a common misconception not helped by the fact that, for years, certain people have been teaching what is essentially kickboxing and passing it off as JKD. A few of the things seperating JKD from boxing/kickboxing is the stance, strong side forward, thumbs up punching techniques, range of fighting, etc.
"Having No Form" versus Having "No-Form"
Over the years many have misinterpreted Bruce's words regarding "no way as way". They practice and teach whatever and then call it JKD. As a result, the actual techniques that Bruce developed are being lost. Failure to master the basic laws of leverage, body position, balance, footwork, and so forth is what Bruce termed "having no form". In other words, ignorance. "No-form", on the other hand, is that level of executing techniques to such perfection that doing so no longer requires thought. (As in the quote from Enter The Dragon..."when there is an opening, I do not hit, it hits all by itself").
JKD is both a philosophy AND a system that Bruce continued to refine until his untimely death. Over the years, some have misinterpreted Bruce's words regarding personal expression to mean "anything goes"-that by taking a little bit of this and a little of that from many different arts, they are then practicing JKD. Ironically, this leads to the very surface knowledge and mechanical conditioning that Bruce was railing against.
And for further evidence of Bruce being against the incorporation of other arts into his JKD system, refer to page 50 of Commentaries on the Martial Way and read the tale of X and Y. That was taken from a letter written by Bruce to his student Jerry Poteet, who wanted to mix JKD drills with kenpo karate. Obviously, Bruce objected.