When things go well, at some point I think we need to ask whether a dog is doing something because 'he wants to', or because he's learned 'he has to'.
But, even if the dog is reliable on a certain 'cue', how does one know 'why' the dog does it - 'wants to', or 'has to'? (One has to ask that question of a species that has co-evolved with humans.) Can you really tell the difference if you haven't trained the dog in question..and even then?
Is it possible a dog does something 'he has to' because 'he wants to'?
I've seen both sides, me thinks. Dogs that experience 'force/pressure' training do something other. Dogs that don't experience 'force/pressure' training do something other.
On both sides of the aisle, I think our own philosophy and training approaches shade our interpretation of the results of our training.
BTW - I think 'Sit' is a wonderful command. There are so many things a dog CAN'T DO while 'sitting'.
Musing...
Chuck
..I can certainly appreciate your thoughts, 'Snick.. nicely said..Thanks for the opportunity to comment..
I think just about everyone begins training pups with the "want to" mindset, and this is how most begin building a great bond with a pup, whether you're a Trialer, in to HT's, Family dog, or a Bird /Duckhunter.. Praise, proper dicipline, and consistantcy with a pup/dog early in life to me..are the main ingredients for a
confident, well rounded retriever later..
In a perfect world, our pups would grow up as dogs and continue those wonderful "want to" desires throughout it's life....
without any kind of pressure at all 
...We just took a break from reality with that thought...Or at least,
I just did 
....
Those cute pups grow up into a
dog..and without any guidance, will only live to please itself, on it's own schedule, it's own agenda, and do things at it's
own convenience, leaving
want to.. a decision all it's own,...and
your "want to's", and desires as secondary, depending on what you're asking of the dog through repetition or attrition..He'll crawl up in your lap because he wants to..but he won't run a blind because he "wants to"...Some things we ask of our dogs aren't auto-programmed from birth..
When things become a "have-to" and the dog becomes more successful having to do it...I begin to see a more confident/successful dawg that will come SIT beside me for a head-scratching moment.. licking my hand in between head scratches.... all because he "wants to" soak up all of the attention, including a good back scratching that's hard to pass up or resist.....
Heck,...he just
had to...... ;-)