In his book, Bruce Lee's Commentaries on the Martial Way, Master Lee talks about the pureness of marial arts from boxing to judo and all warrior arts in between as "they each have therir strong points and weak points. They all need self-evaluation and improvement. They are too narrow-minded. They can only see their strong points. A man confinded in thought and scope will not be able to speak freely. Therefore, if he wants to seek for truth, he should not be condiined by the dead forms."
To conclude, he states that pure forms of martial arts lead to clans who refuse to expand, change, and involve into better systems, just as the martial artist is asked to do. He beleved that the different sytles wasted too much energy dividing, rather than learning from each other.