For a horse to be a dependable ride it must completely subordinate its will to the will of its rider, it must give up all hope of controlling itself. It is surrender that we are working for in training a horse, not trust. Trust and rapport are but steps on the way on the way to achieve the horse's surrender to its rider, regardless of whom that rider may be. A horse will never be a willing partner, but he will be a willing slave. If he was your partner he would be free to negotiate which trail to take, when to stop, what events to enter, but he has no say in any of these things. The horse will never see you as another horse, you will never be his alpha horse, you will always be that two legged thing to him. He will come to terms with you, but you will never be part of his herd.
The horse cannot think, by that I mean that he cannot use reason to reason things out. That is not to say that they do not have good memories, and once they figure something out, like how to unlatch a gate by trial and error. They will remember how they did it when they meet another latched gate. If that way does not work, they will seek another way by trial and error, or give up in defeat. We use their ability to remember to train them to our will. For if they could not remember they would be untrainable.
Horses, all horses, act and react according to the instincts they were born with. We use their instincts to bend their will to ours. By using their natural actions to react in unnatural ways. There is no such thing as Natural Horsemanship, for there is nothing natural about riding a horse. A horse will not naturally accept a bit in his mouth or a saddle upon his back, these are not natural things. Nor is it natural for him to allow a rider upon his back, turn left and right, stop and back up for that rider, and there is no natural way to teach them that.
They are harsh ways, and more gentle ways to train a horse, but there are no natural ways. I use release of pressure as my main training method, the only positive reinforcement I give is released from the pressure I am applying. What type of pressure to apply, and where to apply it comes from understanding a horse's nature, which is no more than to say understanding his instinctual reaction to whatever pressure he may find himself. Fight or flight, resist or comply. We use his natural responses to teach new responses, his natural reaction to build our desired reactions. That is as natural as it get in horse training.