Non-doctrinal rules are often for a season, while their inner truths, or principles, remain invulnerable to age. A de-emphasis of the principles for the sake of the rules seems subtle at first, but soon becomes a tone change that sets the ship off course. The Pharisees were not evil men, but rather determined religious leaders fixed on keeping the Hebrew people pure from paganism. Thou shalt love thy neighbour as thyself. Like U.S. Congressmen, religious leaders on every level find it easier to make rules than to teach principles.
Principles are flexible, sensible and strong.
Non-doctrinal rules grow brittle over time. Principles can be messy and inconsistently applied as people learn to implement them. But they re eternal. When training, their rules are iron-clad and endless as they must learn exactly the best method to shoot, detonate and parachute. Yet, once in the field, all of these fundamentals become subservient to a greater field plan that must adjust to the principles of engagement.