I never tire of reiterating the primacy of the concepts over the form. 
When judging whether a certain movement is WingTsun or not, the deciding factor is whether it agrees with what we call the WingTsun principles. If the motives for performing a movement are incorrect in WT terms, one cannot accept the result to be WingTsun even if it superficially appears to be WingTsun.
It is possible to misinterpret my my strict pronouncement that in the final analysis, the form must follow the function and not vice versa, to mean that I attach no importance whatsoever to the form. Since I also consider the "sections", i.e. the "fixed partner sequences with arm contact" to be forms, or more accurately partner or two-man forms, some readers perspicaciously but still wrongly concluded that I place a low value on them.

Nothing could be further from the truth! I consider the forms, and therefore also the partner forms during Chi-Sao contact, to be indispensable for assured learning progress.
One must always remember that the solo and partner forms, with or without constant arm contact, are not intended as anything but a means to a greater end. The purpose of any self-defence training must always be to acquire the ability to defend oneself.
I have never spoken out against forms as such, but only warned against elevating e.g. sections to the end itself, like some god.
 
Let me also raise a warning finger and remind my readers of one of the darkest periods in modern WingTsun – incidentally not even seven years ago – when certain individuals declared themselves to be holders of the 6th master level in Leung Ting WingTsun for the simple reason that they were able to learn the defined partner forms by heart in 40 or so hours of tuition in Hong Kong.
The fact that even advanced instructors were fooled by this shows that I had done too little explanatory work where the relative value of the "sections" and the other forms was concerned. 
Clearly my publications or statements must have led to the misapprehension that the hard work and feat of memory required to learn certain choreographed movement sequences by heart entitles somebody to claim the master grade whose programme includes the relevant form.
WT veterans may remember that I only ever imparted sections and forms to my students in homeopathic doses, and never the entire section at once, because even then my experience told me that only digestion problems can be the result.
This is because the reactor must not only react, but the initiator must give him the right impulse to prevent the whole thing from becoming counter-productive. As I understand it, form and function must always go hand in hand if we are to get closer to our goal.

So how can form training with or without a cooperative partner help us to improve our self-defence capabilities?
First of all, we must be clear about the relative value of these exercises.
For the sake of clarity, let me compare learning WingTsun with learning a language.
- In this case the 1st form supplies us with the words or vocabulary, some of which it takes us years to learn and use.
- The 2nd form already gives us joined-up words or even mini-sentences.
- The 3rd wooden dummy form provides us with something akin to idiomatic turns of phrase with which we may venture to hold brief sample conversations, if and only if the other party asks the right question.
I will not discuss the 3rd form in this instance, as it follows different rules.
Anybody learning or even teaching a language knows only too well that a flow of conversation requires more than just vocabulary, idiomatic expressions and memorised phrases. It is hardly possible to place words in the correct sequence without having some idea of grammar and syntax.

"But that is what we have our Chi-Sao sections for", I hear you protest in your hunger for confirmation. Well relax, you are quite right to an extent, for Chi-Sao combined with the WT principles really is our grammar and syntax. 
However, what was formerly known as Chi-Sao sequences are not pure Chi-Sao, and not purely tactile reaction training. They are nonetheless a unique creation on the part of Great Grandmaster Leung Ting, and they fulfil another important task: like the games of famous chess grandmasters, they make it possible for us to adopt the thinking of a WT master and follow the principles and their application in detail, as a question-and-answer game. In short, they are model sentences for the rules of our WT grammar.
The more of these model sentences that somebody has absorbed, the more practice material he has available with which to generate new examples.
 
Not all the techniques in these sections are suitable for everybody. While one might suit one person better, another might prefer a different one. I liken it to the display in a supermarket, or the array of tools in a well-equipped toolbox. One of my master students recently referred to the "store of knowledge" of Leung Ting WingTsun, and I think the comparison is apt.
The famous statement by Bruce Lee comes to mind here: Take what you can use, throw away what is not for you. Personally I would add: do not throw it away, but save it for a time when you might need it, either for yourself or your students.
Si-Fu‘s idea went precisely in this direction: the WT student should learn the whole variety of WingTsun so that he can make his personal choice. Those who only practice what their teacher likes best might well miss the technique that might have become their "favourite technique". If they are only able to make their own choice from the choice which the teacher has decided to pass on to his students, the material will become less and less with each succeeding generation, and the art will decline.
In the great store of knowledge that it offered worldwide in all our WingTsun schools, every technique ever passed down is available to every student, and nothing can be forgotten.
Owing to the programmes and sequences – and for the first time in the history of WingTsun, the creation of the sections made it possible for e.g. a university student or anybody else moving from one city or country to another to resume his lessons in a new WT school at the exact point where he was obliged to interrupt them.
This is the great advantage and admirable life achievement which we owe to
Grandmaster Leung Ting.
We must come to regard and employ this valuable learning tool in precisely this way, rather than expecting it to deliver results for which it was never intended. Or would you use a hammer to tighten a screw?