What is 'One Karate'?
No matter the style of Karate, the goals of training should be the same. Primarily Self Defense, then Health, Balance, Flexibility, and so on. As we develop as Karateka and martial artists, no matter what style or point in life you start, we advance towards the same ultimate end. We increase in strength, confidence, knowledge of technique and anatomy, and awareness of our strengths and limitations.
When starting out, different styles of Karate will appear very different. As time goes on and we progress, the differences in Karate's styles will draw closer and closer together, and at the very highest point, at the ultimate height of our practice, there will be no Karate style. Only the pure essence of what Karate is will remain. This is what is meant by One Karate.
This means that we must be willing to learn and practice outside the limitations of our 'style' to progress to the highest point of our potential as Karateka. For example, as my primary style, I began Karate with Shotokan, which emphasizes long deep stances and strikes, which it does very well. In Shotokan's curriculum, there are almost no throws, joint manipulations, or sweeps/ throws. There are some, but not many, or enough to become proficient in this closer range, especially since most Shotokan schools don't practice much grappling. When they do, it's not particularly useful or practical for Self-Defense. However, when you take that same Shotokan curriculum and begin to look at the application and anatomy, the Kata and Bunkai take on an entirely different light. You realize that within the Kata are all the elements that make a martial art useful and practical. They contain attacks and defenses from every range and all angles.
So what style of Karate do you do?
The beginner will answer this in a manner you would expect. "Oh, I do (Shotokan, Wado Ryu, Kyokushin, etc.)." The master of Karate will say, "I practice Karate".
Okay then, what does this 'One Karate' look like?
In essence, the ultimate aim of Karate should be effective practical techniques at any range. This means that I must develop skill in all ranges in my practice, and I must spar in all ranges. I must practice transitioning between all ranges of attack. From Kicks to Punches to the Clinch, Throws, and Grappling. Will I be as good at grappling or throwing as a Jujutsu or Judo practitioner? No, probably not. But I should at least be comfortable enough and confident enough on the ground to protect myself and get up and get away. I must also practice technique, sparring, and defense with and against weapons.