These kinds of discussions are not really resolved in short internet forum discussions. Science is at it's best in physics- as science approaches human affairs it can become easily loaded with more cultural and personal assumptions and models... and becomes loaded with epistemological issues not just verbal definitions. And the context for different issues and meaning a become very important.
You don't have to "believe" in "chi" to do wing chun- just do wing chun "correctly" and chi will take care of itself. The problem is in the meaning of "correctly".Not an easy subject IMO.
In any case, without chi, prana or pneuma- I would be dead. But healthy motion, and many good Asian arts-are helped by an understanding of how the chi flows in motion--if you have a successful acupuncture treatment- it's in part due to the practitioners understanding of the chi flow. The practitioner does not have to use the word chi. Because of Marxist materialism under Mao--they
underused the word chi- but honored TCM and acupuncture.One has to drop both materialistic assumptions and non materialistis assumptions to experiment with what is there in human motion and flow.
You can always tell in taiji in using certain motions- who understands chi in fingers and who doesnt.
CXW in correcting Chen postures personally- before his English got better would say "chi here" at the end of the pathway..
First rate yoga teachers- not the fitness center ones also make sure that your prana(chi) is flowing the right way.
In YGKYM when done well the chi will flow up and down and into your hands and fingers.
Burr's (published) work at Yale in the 1930s experimentally showed that electro- magnetic current runs in all living things.
Licensed DOs-specializing in neuro fascial manipulation also have the working assumption of
a life force being involved in detrmining health or disease.
Interesting as it is one doesn't have to look at the references that Jim is mentioning.
There are different ways of mustering force in a punch- one can be knocked out by 1.a hit by a strong man or Hulk Hogan 2. a punch by a Tyson or 3. a punch by CXW or a top flight wc person.
The potential of #3 takes more training but also last longer in one's life. #1 these days often involve steroids. #2 involves rapid decline after peaking-often leaving some bad side effects on body and mind. The long run of #3 can be diluted by smoking and drinking among other excesses.
Not debating- a considered and devloped opinion and a POV.
joy chaudhuri