An internal Martial art is one in which the power comes from within, from the generation of Ki power (chi power) from the tan tien.
An external Martial Art is one in which the power resides in the muscles.
Now, to be sure, Karate starts out as an external art, but if one practices regularly, and adheres to certain principles, ki power manifests, and the art does become internal, and Karate ki power becomes a reality.
The problem with people recognizing this karate ki power as valid comes from different areas.
First, of course, the common perception. People see people working out, using muscles, and they assume that the art is stuck in muscle, and therefore doesn't progress. Heck, it just doesn't look like what a 'real internal martial art looks like!'
Second is the fact that many people give up their studies at Black Belt, when the doors to ki power begin to open. Thus, they never fully develop, and have only a partial understanding of what is happening.
Third, martial arts like Karate came to this country so fast that there were no qualified teachers who who understood karate ki power and how to make it, or even what it meant. It is a common fact that people in the orient got on the airplane as Green Belts, and got off as black Belts.
The above reasons understood, let's discuss what this karate ki energy is, and how it works, and how to develop it.
Karate Ki power refers to an energy that is spiritual in nature, and which permeates the universe. Indeed, some people would say that the universe is built of ki power, and they wouldn't be far wrong.
Ki power actually works by thought. Once one has become integrated as a human being (which we will explain shortly), mental powers abound, and the power of thought becomes obvious as the reigning influence of the universe. This means things like knowing what is going to happen before it happens, telepathy, even mild (at this time) telekinesis. In short, a whole spectrum of mental powers referred to under the label of 'sixth senses' becomes available to the human being who has achieved Ki Power.
Now, how to get it, how to elevate your karate (or other martial art) to the point where it is internal and manifests this karate ki energy thing.
The most important thing one can do, which will lead one directly to the manifestation of ki power, is to use the body as one unit. This is tossed out glibly in many martial arts, but the direct definition of this phenomena, courtesy of Matrix Martial Arts, is called CBM, or Coordinated Body Motion.
CBM is when one uses all the parts of the body at the same time and in the same direction.
In other words, when doing a martial arts technique (or anything else, for that matter), one puts all body parts in motion at the same time, and in a common direction. And, one stops all body parts at the same time.
This sounds simple, but when one takes into account all the factors, the relative masses and shapes of muscles and so on, it becomes a trick that is best taught by a competent teacher, and through martial arts forms that have been fully matrixed for best effect.
At any rate, once one achieves CBM, and has a Coordinated Body, an amazing phenomena occurs: the mind starts to CBM.
This is what this writer was referring to as an integration of the spirit.
To be sure, one must study, or least exhibit, virtues; virtues are a huge part of the make up of a human being, and we are speaking of an intact and integrated human being here.
But the point is that as one makes the body into an integral machine, one wherein all the parts work together as a single unit, so does the ind begin to work as a single unit, and thus, the human being becomes integrated.
Now, this happens in Karate, and in most classical martial arts, and when this happens the human being becomes ki empowered, he manifest ki power, and his martial art becomes an internal style.
The trick is to keep studying, and to find a martial arts ki system and teacher that encourages the concept of Coordinated Body Motion. I know that some systems encourage this type of energy development. In Aikido Ki is promoted quite intensely, as is chi in Tai Chi Chuan.
But any martial art, even the most eclectic, can be enhanced to the point where they enable human beings to tap into their true abilities and develop karate ki power