Let us continue to learn from a classical Chinese text that was lost for 1000 years, is only partially preserved on bamboo strips, and bears the same title – The Art of War – as the well-known work on strategy by Sun Tzu.
It was written by Sun Bin in the period between 475 and 221 BC, i.e. the author lived after Sun Tzu.
I am quoting the 2nd and final part in full, as it is very hard to find, describes the nature of Chinese strategic thinking in succinct sentences and introduces us to this exotic approach to achieving effectiveness.

Therefore, he who is adept at war can infer from the enemy's advantages his disadvantages. He can also tell where the enemy's strength lies from his own weaknesses. He sees the way to victory as clearly as he sees the sun or the moon. He knows how to win as he knows how to quench fire with water. Using regular warfare is 'Zeng'. Using irregular warfare to combat regular warfare is 'Qi'."
In the WingTsun system we would probably see “Qi“ as the unusual, indirect and non-linear fighting style of the 3rd form (Biu-Tze) in use against the ”conventional” and familiar, linear ”techniques” from the other forms .

"There is no end to the interchange between 'Qi' and 'Zheng'. It all depends on how to deploy your forces. Assign the different units with 'Qi' and 'Zheng' tasks and use the law of mutual checks among the five elements to cope with the enemy."
This is another reference to a popular but rather nebulous topic in the Chinese martial arts, the so-called “Five Elements“ (earth, water, wood, fire, metal) on which the harmony of the world is said to be based by the interaction between the ”principles of Yin and Yang“ and the ”Pa-Kua theory“. As WingTsun dismisses the theory of the five elements and Pa-Kua as superstition (according to the views of Sifu Leung Ting, Golden Level WingTsun), I will not dwell on these unscientific, non- WingTsun related ideas any further. 

"Once the deployment is decided on, the formation takes shape; and once the formations take shape, they will be recognizable; and once they are recognized ..."
This sentence has not been fully preserved, but we are able to complete it without difficulty: “Once the form becomes recognisable“ – it can be defeated.

"If you use the same battle formation every time, you will not win victory. Only when you use different formations in different circumstances will you be able to defeat the enemy by a surprise move."
This is a clear warning not to adopt any form to which the opponent can adapt himself before an encounter.

"Thus, I shall give the enemy an impression of inaction and then take him by surprise; the impression of being tired when in fact I am rested; of being starved when in fact well-fed; of confusion in the army when in fact there is order; and of being few in number when in fact my troops are many."
Disguise and deception, making the enemy believe what is not and concealing what is – these are already familiar to us from Sun Tzu’s ”Art of War“.

"Any move that is detected by the enemy is 'Zheng', that which is undetected is 'Qi'. Victory is assured when the enemy is caught unawares and unprepared."
This clearly states that an action is not e.g. “Qi“ on its own account. Merely using a non-linear, indirect “technique“ does not make the action itself “Qi”. If the opponent is not surprised by it, possibly because non-linear movements are what he is accustomed to, then a move that might surprise linear stylists (“Qi“) only remains ”Zheng“, a technique that merely elicits a yawn because he has been confronted with it thousands of times.

"Once you have mastered the way of defeating the enemy by surprise moves, you will be able to win great victories."

With this final sentence, to which nothing needs to be added for clarity, we will take our leave of Sun Bin and never forget that only surprise and confusing, spontaneous actions are the key to success:

• If I am fighting somebody who is unfamiliar with WT, orthodox WT methods and even prefabricated "attacking techniques" can certainly be a successful method by virtue of surprise.

• But adopting the usual WT fighting stance and using normal WT “techniques“ would come as no surprise to another WT fighter, and would therefore not be a sure way to success. Prevailing against another WingTsun fighter either requires much greater skill (e.g. sense of distance, tactile sensitivity, timing: experience) or surprising, spontaneous movements.

Kindest regards

Your
SiFu, SiGung ...

Keith R. Kernspecht