The great Bruce Lee in this 1965 interview:
"Well, it's bad to say the best, but in my opinion, I think Kung Fu is pretty good….[To explain] Kung Fu, the best example would be a glass of water. Why? Because water is the softest substance in the world, but yet it can penetrate the hardest rock… Water also is insubstantial. By that I mean you cannot grasp nor hold it."