Wing Chun is a Fist Arts therefore the logic behind it is Fist Logic, which at its most instinctive level simply hits things. Wing Chun is first and foremost about hitting people. No matter what drill or activity we are involved in we should always measure it by the Fist Logic metrics of Simplicity, Practicality, Directness, Economy of Movement and Minimal use of Brute Force.
The five main Logics are not stand alone ideas, we cannot use one or two and ignore the rest, if we claim to do Wing Chun they must all be present. They are “The Five Principles” and as close as Wing Chun comes to dogma.
There are sub logics that evolve from combinations of the Five, sub logics are not so strict as the Five and allow some latitude, exceptions to the rule because reality is never like training.
Simultaneous defence and attack is a Sub Logic that is paramount to the Wing Chun Idea, where ever possible this approach is taken literally but in its wider sense it means hit at the earliest opportunity.
Another important sub logic is never using two arms to defend against one, we cannot implement simultaneous defence and attack if both arms are defending, in its wider sense though we can use two Lan Sau’s or Jit Sau’s to ward of a stick or high kick, we can employ a double Lap Sau to propel someone into an obstacle or a wall.
Once we seriously consider our actions by this metric, which means become serious and honest about Wing Chun it becomes clear that any action where a Bong Sau is used for defence is not working in accord with the Five, Bong Sau defies Fist Logic and if we can see past the theatre that is Chi Sau this means that it is not a working Wing Chun option. Thinking that Bong Sau is a viable option leads into all kinds of bad practice and misunderstanding, that infects all of the Chi Sau drills, the understanding that many students end up with from the Lap Sau drill also defies Fist Logic, and as such Wing Chun because there is a moment where we use two arms to defend against one.
Other important sub logics are to never fight force with force, to never carry our opponents weight, but Chi Sau play ignores this to a large extent as we grind, grind, chug, chug. If we cannot see drills for what they are then they become something they are not and where never meant to be, they become a parody that only works with friends in the training hall and they fail to deliver the intended result when it is really needed. We need to see the seductive safety and elevated opinion of Chi Sau practice for what it really is.