A *ming* teacher is not just a teacher who can remember forms and perform them back to you like a video recorder.
Being able to remember forms helps you to master Tai Chi but its not enough. You must penetrate to the essence of the forms and live them to be able to say you understand them. Otherwise, your movements will be souless and tasteless. You will not be able to use the techniques freely within push hands not to mention combat.
To know a form is not to just know the movements. To know a form means to know :-
a) The principles on their own and as a whole
b) The nuances and details of each movement
c) The obvious, hidden and derived applications of the movement
d) The ways of neutralizing and issuing
e) Able to express innumerable changes
f) Concealing complexity within simplicity, concealing intent
Take an example – Cross Hands :-
a) What are the principles at play in Cross Hands
b) What are the nuances and details to express and cultivate in our practice?
c) What are the many ways to use Cross Hands?
d) How can Cross Hands be used to neutralize and issue power?
e) How can Cross Hands express innumerable changes?
f) What is the intent in Cross Hands? How to conceal it?
So, do you *ming* (understand) Cross Hands?
If you can give good, consistent and comprehensive answers as well as able to apply Cross Hands, even in push hands then you can say you at least understand something about Tai Chi.