Resolved: The only one who can teach you to ride is a horse.
Pro: Riding is all about feel. No amount of third-party yelling will force you to feel until you are ready.
Con: Poor riding is not self-correcting. A good instructor will smooth the bad and highlight the good.
Where do you come down on this question?
Virtual Brush Box 
Yes, the horse is the chief instructor, but a ground-level person is often (in fact usually) needed to translate what the horse is saying. Riding is as much about communication as it is about feel.
How about both?
Having someone explain what you are feeling is critical. You can feel all the feels, but knowing what is a good feel and what is a bad feel doesn’t “come naturally.” Can you remember the first time you actually felt a horse come into the contact? I do; I had been riding all of my life at that point (I was 25), but was taking my first dressage lesson with a BNT on a schoolmaster. I had a vague idea of what “on the bit” was supposed to be, but hadn’t really the first notion about what it would feel like, or how to find that contact. I was a solid hunt seat rider at that point, with a good seat and soft hands. Instructor explained what we were going for, talked me through it, and when it happened, it was like magic. That feeling has stayed with me for 26 years now and *instantly* made me realize where I wanted to go with my riding (away from perching, and toward a real connection with the horse).
That said, become a strong, *independent* rider comes from being able to take instruction and use it on your own. You cannot be a strong rider riding once a week. To develop a true core and feel, you need to ride on your own, develop a great seat, solid position and learn to feel on your own when things are going south.
I wrote about The Golden Pathway in my first book: the basic concept is that a riding lesson puts you on the Golden Pathway, where all is right with the world and you are riding to beat the band … but when you are on your own, and you are only hearing the booming voice of your instructor echoing in your head, things start to drift … that’s basically how I ride these days. One lesson a week, to keep me on the Golden Pathway, the rest of the time, I’m on my own, making my own mistakes, but also having my own victories.
Not much of a debate. You all agree,