Historically  and for good reason...

 The lowest arts is a matter of reflex , you see something THEN u respond , relying on your eyes, you are always playing catch up no matter how fast you can move

 The second level is you touch something , you feel it, and it respond , this way is much faster since your sense of touch is biologically much faster than your sense of sight

 The highest level is you feel something before you even touch it and you respond, this is the fastest

 The problem is that during a friendly demo , the lowest and the highest may look the same to the novice because both operates without touch , but in reality they are worlds apart...   

And so when people think that they can do third level stuff without the second level , well thats just crazy..... and to justify incompetence by quoting those who came before is just silly - this silliness is the number one danger of hero/founder worship in MA.....

None of the 3 levels are things u have to get , they are all inborn for most ( the ability to see, to feel through touch, to feel without touch) , all training does is  it  amplifies it to the maximum of your potential , which is saying a lot....

 Summary in martial terms...  

level 1: you see and then you react ( reflex , common in all sports and all eye hand co-ordination activities)

level 2 you touch, feel and respond  ( sticking , chi sau , free hands, push hands , rolling hands etc etc)

level 3 you feel without touch and respond  ( chi gung stuff and the fusion of it to martial arts)

are the progression block  for each?

level 1 is usually not block -  99% of martial arts is this and it is great and fun 

level 2 is block when people think they can by pass it without spending any time on it; much like how some people think they can judge someone without getting to know them first - simply illogical .....  

level 3 is 99.9% block for most simply because of disbelief and therefore not allowing themselves to even try it  for 10 minutes !

The most important thing about level 2 and  3 is that they are the only levels in MA where peaceful -oneness philosophies are no longer lip service but rather direct body sensation and therefore finally a reality.....