True, Bruce Lee did say that JKD is not a style, but we have to look at the context in which he said it. At the time, martial arts were very rigidly set in tradition with very specific rules and limits.
Bruce Lee had concern about calling JKD a “style” because he believed that styles separate and limit people rather than bring people together. What he did not want is that the student might not actively participate in the learning process at a deep level thinking that he is not qualified to question or test the ways of “the style”; nor did he want JKD to become heavily commercialized where the individual experience was forsaken in favor of mass appeal. Bruce Lee wanted to avoid “killing” JKD by saying there was a definite beginning and end to the process. Rather he viewed JKD as a never-ending process – a living and breathing thing that would add more and more meaning to the practitioner the deeper he delved into his practice.
Bruce Lee believed JKD was a particular system comprised of systematic, methodical, empirically tested techniques. In Lee’s private notes and in correspondence with friends he saw JKD as having certain core elements that set it apart from other martial arts. In his own words, “There is always a most efficient and alive manner to carry out a movement (and that the basic laws of leverage, body position, balance, footwork, and so forth, are not to be violated).” The specifics of these are the principles that form the core elements of JFJKD.