This year we are discussing the Book of Martial Power (BOMP) on Saturdays.
Ever been around hyperactive kids about 4 or 5 or 6-years old? Ever had what I affectionately call, "a Pediatric Projectile," fire itself headfirst into your groin? I'm talking about a running, jumping, flying headbutt into the crotch. If you haven't experienced this one then you haven't been around kids that much. The moral of that little vignette is that we all (even small kids) have a tremendous amount of potential energy stored in our bodies at all times.
Fortunately (for parents) and unfortunately (for martial artists), we are only ever able to communicate a fraction of that energy as offensive power. If kids ever figured out how to communicate 100% of their energy directly into your groin then we'd have to chain them all up in a bunker and slap WMD (Weapons of Male Destruction) stickers on them.
On the other hand, if a martial artist can learn how to use a higher fraction of his own power then he has a greater chance of defeating a Gargantua who (we presume) will be using a much smaller fraction of his (presumably) much larger power.
Just to put numbers to it, consider Jigoro Kano's famous example...
Let us say that the strength of this man is 10 units, whereas my strength, less than his, is 7 units. Then if he pushes me with all his force, I shall certainly be pushed back or thrown down, even if I use all my strength against him. This would happen from opposing strength to strength. But if instead of opposing him, I leave him unresisted, withdrawing my body just as much as he pushes, at the same time keeping my balance, he will naturally lean forward and lose his balance. In this new position, he may become weak (not in actual physical strength, but because of his awkward position) as to reduce his strength for the moment, say to 3 units only instead of 10 units. But meanwhile I, by keeping my balance, retain my full strength, as originally represented by 7 units. Here then, I am momentarily in a superior position, and I can defeat my opponent by using only half of my strength, or 3 1/2 units against his 3 units. This leaves one-half of my strength available for any other purpose. If I had greater strength than my opponent, I could of course push him back. But even if I wished to and had the power to do so, it would still be better for me first to give way, because by so doing, I should have greatly saved my energy and exhausted my opponent's.
That is a near perfect example/explanation of Pearlman's Percentage Principle. I say near-perfect, because it still appears to me that Kano is talking about yielding and breaking the opponent's balance, which is (as in Pearlman's previous chapter, shortening the opponent's line instead of lengthening ours.
But anyway, The Percentage Principle is that...
We must strive to learn to communicate near 100% of whatever our own potential power is, and in so doing, we have the possibility of defeating an opponent with larger potential but poorer utilization of that potential.