Re: Ki to the Highway
There are quite a number of words that denote an important domain of our experience in spite of our inability to say what it is exactly they refer to. Some would argue "Death" is one. Or the everyday uses of "Energy".
Many find them very useful in spite of not being able to (and maybe not seeing a need to) define their meaning precisely. They will be replaced if something more useful turns up. I would suspect that is a practical matter, really.