空手は外家拳である。主には，あるいは，始めには，筋力と瞬発力を用い，パワーとスピードでもって敵を制するような術を身につけることを目的とする。つまり，剛の拳である。剛の拳は，鍛えるべきところが外面的であるために，目に見えるために分かりやすい。そのために，まずは武術として分かりやすい外家拳から入る，という人は多い。
空手と称する各種流派の中でその最たるところが，極真である。極真は「パワー空手」と自称するほど自覚的にパワーとスピードを求める。まるでボディービルダーと見紛うばかりの極真家を見かけることがある。つまり，究極の剛の拳を目指す。これはこれで，目標が非常に明確であり，その端的さシンプルさが，率直なまでに，格闘における強さを証明している。極真あるいはその系統であるフルコンタクト空手諸派は，ストリートファイトには滅法強いであろう。
速く突く，強く突く，速く蹴る，強く蹴る，高く蹴る，という目標は，外面的に誰から見ても一目瞭然であり，分かりやすい。だから，まずは外家拳あるいは剛の拳というのに取り組む，というアプローチは自然である。
しかし，武術の「術」としての本質は，そうした筋的な強さstrengthや力powerだとか，あるいは瞬発的なスピードspeedや反射reflexではない。むしろ，自己と他者のエナジーをどう導くか，というところにある。つまり，energyとdirectionである。それが術であり，その術を習い，養うところに，本来の主眼と醍醐味がある。
そのことを最初から求めているのが，太極拳や合気系武術のような，内家拳，あるいは柔の拳である。太極拳や合気系武術の術理のポイントは，エナジーをどう導くか，というところにある。
もちろん，究極的には，武術に外も内もない。外家拳から入った武術家も，正しく歩んでいれば，いずれ内（柔）へと至る。逆も然りであり，内家拳から入った武術家も，外（剛）の重要性に気づく。そして最後には同じところに行き着くはずである。内と外，剛と柔を兼ね備え，統一され，融合され，全体として「一」となるところに，武術の理想的姿がある。それはまさに陰と陽が混ざり合い，やがて一となる，陰陽は一に存在する，というのと同じである。
Karate is an external martial art. Mainly or firstly, the purpose of the practice is to learn such arts as controlling enemies with power and speed by using muscular strength and instantaneous force. That is a hard martial art. The hard arts is easy to understand because the parts that should be practiced are external and visible. Then, there are a lot of people, who first begin to practice any external martial art because it is understandable in terms of martial arts.
The most external among various schools of so called "karate" is Kyokushin. Practitioners of Kyokushin are consciously aiming at power and speed as they call their own style "power karate". Sometimes we can see a Kyokushin-ka (Kyokushin karate practitioner), who looks as if he were a body-builder or something. That is, they aims at an ultimate hard martial art. This aim itself is very clear, and it is so simple and straightforward that it can directly prove that Kyokushin is superior than other schools in a combative scene. Kyokushin or various "full-contact karate" schools deriving from it can get the upper hand in street fighting.
Such aims as punching quickly and strongly, or kicking quickly, strongly, and highly are externally clear for anyone at a glance, and then understandable. Then, it is natural for people to adopt an approach in which at first they begin to learn external martial arts or hard martial arts.
However, the essence of martial arts as it is "arts" is not such as muscular strength and power, nor instantaneous speed and reflex. Rather, the essence is found at how we can direct the energy of ourselves and others. So that means the essence is energy and direction. That is arts, and it is learning and cultivating the arts that is the essential focus and joy of martial arts.
It is internal martial arts or soft martial arts such as Tai Chi or aiki-originated martial arts that aim at the essence from the beginning. The point of the theories that Tai Chi or aiki-originated martial arts have is in how the energy is directed.
Of course, ultimately, martial arts is neither external nor internal. If even people, who had begun to practice external martial arts, progressed in a right way, they would eventually come to the internal (soft). The reverse is also true. Martial artists, who began to practice internal arts, would notice the importance of the external (hard). And then, all of them are supposed to arrive at the same place at the end. There is an ideal of martial arts existing at the state where the artists have both the internal and external, or the hard and soft, which are unified, integrated, and become a whole "one". That is the same as the state yin and yang merge together, and then become one, that is, yin and yang exist as one.
