That is indeed true! So what does this mean?
Does this mean that whatever it is ineffective, because I cannot do it? Or does it mean that I don't know how to make it work?
Neither. It means it is time for more investigation.
It sounds like a cop out, but it isn't. We look to others - we see if people with similar physical traits can make the technique or principle work according to the 3 Cs I mentioned earlier, and then decide whether or not to train it for ourselves. (This is called this SYSTEMS PRESSURE TESTING.) If we train it for ourselves, we then test personal ability to perform the technique. (This is called PERSONAL PRESSURE TESTING).
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Let me give a hypothetical example. Let us say that I am a very obese man and I have poor leg flexibility. One person says "fat people can't kick high," another tells me it is still quite anatomically possible. I look to PRIDE FC, and notice the very overweight Mark Hunt performing sucessful highkicks, and conclude that it will be possible for me to lose some weight, limber up, gradually develop flexiblity, and eventually kick high. (systems pressure testing testing)
Hypothetically, I would then find a competent teacher who guides me through this process, and I periodically test my progress by kicking high at opportune moments in sparring. Perhaps I am sucessful - then I have added a weapon to my abilities. Perhaps I am unsucessful - then I will know, I can ditch that training and do something more productive. (Personal pressure testing)
The reason this works is that the systems pressure testing establishes it as probable, improbable, or impossible, and then personal pressure testing establishes that I personally can do it. In the example, I don't simply draw a conclusion based on my present circumstances, nor do I take the word of any person. I look for evidence for and against each side, and then test whether that applies to me or not.