Wow ... great responses all ... breath of fresh air actually to get some critical thinking rather than the carry on the Tai Chi folks make about this.
I apologize in advance if I don't address your comments directly here...
OK so here is the "claim":
Michael Phillips, and those of the same persuasion, claim that through the "non-bio-mechanical" power of Fajin they can "bounce" opponents away (regardless of opponent size or environmental factors) with ONLY the lightest touch of the opponent's fingertips touching the forearms of the demonstrator (see 8:15 Mysteries of Tai Chi Chuan - Part 1 of 3).
To be clear this is Michael's description:
“The outward sign of fajin is that the wrists and elbows of the person issuing fa-jin do not follow the opponent, as they would if one were merely "pushing" with the muscles - in Chinese, this is called "The arrow is fired, but the bow remains." The real test is to stand with one's feet parallel with someone at least your own size facing you in a well-rooted bow-stance, and instantly shear him off his feet, both feet clear off the ground in a single moment, and send him backwards 3-4 feet with his feet ending in the same alignment. All of this done with the demonstrator having no discernible tension in one's shoulders, elbows, or wrists.
Whilst there may be a visible "pulse-wave" passing thru the body-system, if someones elbow accelerates forward and follows the trajectory of the opponent as he is thrown backwards, what has just occurred is definitely NOT [Tai Chi] fajin!"
Michael claims that this is NOT based on "normal" bio-mechanics (see 8:43 Mysteries of Tai Chi Chuan - Part 1 of 3) and that there is absolutely no muscular strength (commonly called "external strength" as opposed to the "internal strength" fajin that Michael claims to be proficient at) being used in the technique.
In conversation with Michael and other "believers" they claim repeatedly, and rather obtusely, that this fajin is beyond the scope of normal scientific understanding or explanation thus, at least in my mind, fulfilling the requirement of it being a claim of paranormal ability.