Familiarity with each of the "Four ranges of combat", in particular, is thought to be instrumental in becoming a "total" martial artist. JKD teaches that the best defense is a strong offense, hence the principle of an "intercepting fist". For someone to attack another hand-to-hand, the attacker must approach the target. This provides an opportunity for the attacked person to "intercept" the attacking movement. The principle of interception may be applied to more than intercepting physical attacks; non-verbal cues (subtle movements that an opponent may be unaware of) may also be perceived or "intercepted", and thus be used to one's advantage. The "Five ways of attack", categories which help JKD practitioners organize their fighting repertoire, comprise the offensive teachings of JKD. The concepts of "Stop hits & stop kicks", and "Simultaneous parrying & punching", based on the concept of single fluid motions which attack while defending (in systems such as Épée fencing and Wing Chun), compose the defensive teachings of JKD. These concepts were modified for unarmed combat and implemented into the JKD framework by Lee to complement the principle of interception.